Article

B-Site-Ordered and Disordered Structures in A-Site-Ordered

Quadruple Perovskites RMn3Ni2Mn2O12 with R = Nd, Sm, Gd,
and Dy
Alexei A. Belik 1, * , Ran Liu 1,2,3 , Masahiko Tanaka 4 and Kazunari Yamaura 1,2

1 Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS),
Namiki 1-1, Tsukuba 305-0044, Ibaraki, Japan; liu.ran@sanken.osaka-u.ac.jp (R.L.);
yamaura.kazunari@nims.go.jp (K.Y.)
2 Graduate School of Chemical Sciences and Engineering, Hokkaido University, North 10 West 8, Kita-ku,
Sapporo 060-0810, Hokkaido, Japan
3 Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1,
Ibaraki 567-0047, Osaka, Japan
4 National Institute for Materials Science (NIMS), Sengen 1-2-1, Tsukuba 305-0047, Ibaraki, Japan;
tanaka.masahiko@nims.go.jp
* Correspondence: alexei.belik@nims.go.jp

Abstract: ABO3 perovskite materials with small cations at the A site, especially with ordered
cation arrangements, have attracted a lot of interest because they show unusual physical prop-
erties and deviations from general perovskite tendencies. In this work, A-site-ordered quadruple
perovskites, RMn3 Ni2 Mn2 O12 with R = Nd, Sm, Gd, and Dy, were synthesized by a high-pressure,
high-temperature method at about 6 GPa. Annealing at about 1500 K produced samples with addi-
tional (partial) B-site ordering of Ni2+ and Mn4+ cations, crystallizing in space group Pn–3. Annealing
at about 1700 K produced samples with disordering of Ni2+ and Mn4+ cations, crystallizing in space
group Im–3. However, magnetic properties were nearly identical for the Pn–3 and Im–3 modifications
in comparison with ferromagnetic double perovskites R2 NiMnO6 , where the degree of Ni2+ and Mn4+
ordering has significant effects on magnetic properties. In RMn3 Ni2 Mn2 O12 , one magnetic transition
was found at 26 K (for R = Nd), 23 K (for R = Sm), and 22 K (for R = Gd), and two transitions were
Citation: Belik, A.A.; Liu, R.; Tanaka,
found at 10 K and 36 K for R = Dy. Curie–Weiss temperatures were close to zero in all compounds,
M.; Yamaura, K. B-Site-Ordered and
Disordered Structures in A-Site-
suggesting that antiferromagnetic and ferromagnetic interactions are of the same magnitude.
Ordered Quadruple Perovskites
RMn3 Ni2 Mn2 O12 with R = Nd, Sm, Keywords: A-site-ordered quadruple perovskites; B-site double ordering; crystal structures;
Gd, and Dy. Molecules 2024, 29, 5488. structural disorder
https://doi.org/10.3390/molecules
29235488

Academic Editor: Marco Anni

1. Introduction
Received: 10 October 2024 Perovskite-structure materials with a variety of cation orders attract a lot of attention,
Revised: 15 November 2024 as properties can be tuned through different degrees of ordering. There are large subfamilies
Accepted: 18 November 2024 of perovskite-structure cation-ordered materials, for example, B-site double perovskites,
Published: 21 November 2024 A2 B′ B′′ O6 [1], and A-site-ordered quadruple perovskites, AA′ 3 B4 O12 [2–7]. There are
more than one thousand examples of different A2 B′ B′′ O6 perovskites [1] and hundreds of
AA′ 3 B4 O12 perovskites [2–7].
Copyright: © 2024 by the authors.
Among different possible combinations of B′ and B′′ cations in A2 B′ B′′ O6 , a combi-
Licensee MDPI, Basel, Switzerland.
nation of B′ = Ni2+ and B′′ = Mn4+ attracts special attention as such a combination can
This article is an open access article
produce ferromagnetic (FM) properties according to the Goodenough–Kanamori rules [8].
distributed under the terms and R2 NiMnO6 perovskites, where R is a rare-earth element, were investigated a lot [9–29], and
conditions of the Creative Commons FM properties were indeed observed for all members from R = La (TC ≈ 280 K [10,17,19]) to
Attribution (CC BY) license (https:// R = Lu (TC ≈ 40 K [18,19,25,26,28]). The FM Curie temperature, TC , decreases in R2 NiMnO6
creativecommons.org/licenses/by/ as the deviation of the Ni–O–Mn bond angles increases from 180◦ [25,28]. In addition,
4.0/). the degree of Ni2+ and Mn4+ cation ordering in R2 NiMnO6 has significant effects on the

Molecules 2024, 29, 5488. https://doi.org/10.3390/molecules29235488 https://www.mdpi.com/journal/molecules

Molecules 2024, 29, 5488 2 of 17

FM properties [9,18]. Near-room-temperature magnetocapacitance and magnetoresistance

effects were observed in La2 NiMnO6 [10,12,13].
The introduction of other cations [smaller than Lu3+ (rXIII (Lu3+ ) = 0.977 Å [30]), such
as In3+ with rXIII (In3+ ) = 0.92 Å [30], Sc3+ with rXIII (Sc3+ ) = 0.870 Å [30], and Mn2+ with
rXIII (Mn2+ ) = 0.96 Å [30])] into the A sites further reduces B–O–B′ bond angles and decreases
the strength of direct B–B′ exchange interactions and can produce “exotic” properties [7,31].
For example, In2 NiMnO6 already shows a complex incommensurate antiferromagnetic
(AFM) ordering at TN = 26 K and spin-induced ferroelectric polarization [21] in comparison
with FM properties of R2 NiMnO6 . Sc2 NiMnO6 demonstrates two AFM transitions and a
complex magnetodielectric response [22]. Lu2 NiMnO6 is located near a phase boundary,
and external effects, such as moderate pressure, can induce a transition to an incommensu-
rate AFM order from an FM order [25].
B-site double perovskites, A2 B′ B′′ O6 , and A-site-ordered quadruple perovskites,
AA′ 3 B4 O12 , can be combined to simultaneously produce A-site- and B-site-ordered struc-
tures, AA′ 3 B′ 2 B′′ 2O12 [32–46]. Depending on the combinations of B′ and B′′ cations, such
AA′ 3 B’2 B′′ 2O12 perovskites can show large ferrimagnetic transitions above room temper-
ature [35,37] and half-metallic properties [37,41]. In addition, such perovskites can show
good catalytic properties [4], as they contain transition metals in different oxidation states
and exotic magnetic ground states [28].
The R2 NiMnO6 family of double perovskites was recently extended further through
the synthesis of an AA′ 3 B′ 2 B′′ 2O12 -type perovskite, LaMn3 Ni2 Mn2 O12 [28]. The average
size of La3+ and 3Mn3+ cations is small; therefore, LaMn3 Ni2 Mn2 O12 falls into the region
with “exotic” properties, as Ni–O–Mn bond angles deviate significantly from 180◦ [28].
Two magnetic transitions were found in LaMn3 Ni2 Mn2 O12 in comparison with other
members of the R2 NiMnO6 family (R = La–Lu), and complex magnetic structures were
realized [28,29].
In this work, we prepared and investigated other members of RMn3 Ni2 Mn2 O12 per-
ovskites with R = Nd, Sm, Gd, and Dy, where the average size of R3+ and 3Mn3+ cations is
further reduced (Table 1). In addition, we prepared two modifications of RMn3 Ni2 Mn2 O12
perovskites with R = Nd and Sm, one with B-site ordering and the second without B-site
ordering, and investigated the effects of B-site ordering on magnetic properties.

Table 1. A list of RMn3 Ni2 Mn2 O12 samples prepared (at a high pressure of 6 GPa) and investigated
in this work.

R Synthesis Temperature Symmetry

Nd 1500 K Pn–3
Nd 1700 K Im–3
Sm 1500 K Pn–3
Sm 1700 K Im–3
Gd 1500 K Pn–3
Dy 1500 K Pn–3

2. Results and Discussion

RMn3 Ni2 Mn2 O12 samples with R = Nd, Sm, Gd, and Dy prepared at 1500 K crystal-
lized in space group Pn–3 because of the observation of a (311) reflection on synchrotron
XRPD data (Figure 1). The Pn–3 structure has two B sites and corresponds to an ordered
arrangement of Ni2+ and Mn4+ cations (or at least partial ordering). The distribution of
Ni2+ and Mn4+ cations between the two sites was refined with constraints on the full site
occupation and the total chemical compositions. All the samples showed nearly the same
refined occupation factors of 0.8Ni2+ + 0.2Mn4+ for the B site and 0.2Ni2+ + 0.8Mn4+ for the
B′ site, suggesting a significant degree of Ni2+ and Mn4+ ordering. We also checked the
occupation factors (g) of the R site and found that it was very close to 1 (g(Nd) = 1.0013(12),
g(Sm) = 0.9994(11), g(Gd) = 1.0057(13), and g(Dy) = 1.0026(11)). Therefore, the occupa-
tion factor of the R site was fixed at 1 in the final models. All the samples contained a
Molecules 2024, 29, x FOR PEER REVIEW 3 of 17

Molecules 2024, 29, 5488 3 of 17

factor of the R site was fixed at 1 in the final models. All the samples contained a small
amount of NiOof impurity;
small amount the appearance
NiO impurity; of NiO
the appearance of NiOimpurity
impurity was also
was alsoobserved
observedinin
LaMn
LaMn3 Ni2 Mn2 O12 [28]. The refined structural parameters and primary bond lengthsfor
3 Ni 2Mn 2 O12 [28]. The refined structural parameters and primary bond lengths for
RMn
RMn 3Ni 2Mn2O12-Pn–3 are summarized in Tables 2 and 3. Experimental, calculated, and
3 Ni2 Mn2 O12 -Pn–3 are summarized in Tables 2 and 3. Experimental, calculated, and
difference
differencesynchrotron
synchrotronXRPDXRPDpatterns
patternsare
are shown
shown in
in Figure
Figure 11 for
for NdMn
NdMn33Ni
Ni22Mn
Mn22OO1212-Pn–3
-Pn–3
asasan
anexample.
example.

Experimental(black
Figure1.1.Experimental
Figure (blackcrosses),
crosses),calculated
calculated(red
(redline),
line),and
anddifference
difference(blue
(blueline
lineatatthe
thebottom)
bottom)
room-temperaturesynchrotron
room-temperature synchrotronX-rayX-raypowder
powder diffraction
diffraction patterns
patterns ofof NdMn33Ni Ni22Mn
Mn22OO1212(in
(inthe Pn–3
thePn–3
modification, prepared at 1500 K) in a 2θ range of 6°◦and 59°.◦ The tick marks show
modification, prepared at 1500 K) in a 2θ range of 6 and 59 . The tick marks show possible Bragg possible Bragg
reflection
reflectionpositions for the
positions for themain
mainphase
phase and
and NiO
NiO impurity
impurity (from(from top
top to to bottom).
bottom). Inset shows
Inset shows a zoomed a
zoomed part in a 2θ range
◦ of 16° and
◦ 17.8° and emphasizes the presence of the (311) reflection
part in a 2θ range of 16 and 17.8 and emphasizes the presence of the (311) reflection from the B-site from
the B-site ordering. Inset shows a scanning electron microscopy (SEM) image, where the scale bar is
ordering. Inset shows a scanning electron microscopy (SEM) image, where the scale bar is 20 µm.
20 µm.
The accuracy of determination of distributions of Ni2+ and Mn4+ cations with syn-
Table 2. Structure parameters of RMn3Ni2Mn2O12 (Pn–3; prepared at 1500 K) at room temperature
chrotron XRPD is, of course, much lower than with neutron diffraction [28]. Nevertheless,
from synchrotron powder X-ray diffraction 2+
data. 4+
with the obtained distributions of Ni and Mn cations, the refined isotropic atomic
displacement R parameters ofNd the Ni1 and Mn2Sm sites were almost Gdcomparable toDy each other
(about 0.4 Å 2 ) for all compounds. On the other hand, the refined isotropic atomic dis-
a (Å) 7.35504(1) 7.34371(1) 7.33561(1) 7.32757(1)
placement 2+ and Mn4+
V (Åparameters
3) were quite different396.0468(5)
397.8824(2) for two extreme394.7375(5)
distributions of Ni
393.4419(4)
cations:
Biso(R) B(Ni(Å 1)) = 0.78(3) Å
2 2 and B(Mn2 ) =0.532(5)
0.436(5) 2
−0.05(2) Å for0.551(6)
the full cation ordering
0.661(5) and
B(NiB1iso)(Mn 2
SQ) (Å2)Å and B(Mn
= 0.11(2) 2 for the full cation
2 ) = 0.65(3) Å 0.578(8)
0.541(9) disordering (for
0.560(9) the R = Nd
0.550(7)
sample as an example). 0.82(2)Ni+ 0.834(17)Ni+ 0.82(2)Ni+ 0.831(16)Ni+
g(Ni1/Mn1)
RMn3 Ni2 Mn2 O12 samples 0.18Mnwith R = Nd 0.166Mn
and Sm prepared 0.18Mn 0.169Mn
at 1700 K crystallized in
Biso(Ni
space 1/Mn1)
group (Å2) because0.36(4)
Im–3 of the absence of0.42(4)
a (311) reflection0.34(4)
on synchrotron0.38(3)
XRPD data
(Figure 2).2/Ni
The 0.82Mn+
Im–3 structure 0.834Mn+
has one B site and, therefore,0.82Mn+
corresponds to0.831Mn+
a disordered
g(Mn 2)
arrangement of Ni2+ and Mn 4+ cations. The refined
0.18Ni 0.166Ni structural 0.18Ni 0.169Ni bond
parameters and primary
Biso(Mnfor
lengths 2/Ni2) (Å2)
RMn3 Ni2 Mn2 O0.38(4) 0.36(4) 0.45(4) 0.34(4)
12 -Im–3 are summarized in Table 4. Experimental, calculated,
x(O) 0.2576(5) 0.2576(5) 0.2576(6)
and difference synchrotron XRPD patterns are shown in Figure 2 for NdMn3 Ni2 Mn2 O12 - 0.2574(5)
Im–3 as y(O) an example. RMn 0.42527(16) 0.42542(16) 0.42462(19)
3 Ni2 Mn2 O12 samples with R = Nd and Sm prepared at 1700 K
0.42412(16)
z(O) 0.55854(15) 0.55767(14) 0.55771(17)
crystallized in space group Im–3 because of the absence of a (311) reflection on 0.55632(14)
synchrotron
B iso(O) (Å2) 0.49(3) 0.62(3) 0.54(3)
XRPD data (Figure 2). The Im–3 structure has one B site and, therefore, corresponds 0.60(3) to
Rwp (%) 3.66 4.17 4.66 4.85
the disordered arrangement of Ni2+ and Mn 4+ cations. Experimental, calculated, and
Rp (%) 2.40 2.78 2.87 3.32
difference synchrotron XRPD patterns are shown in Figure 2 for NdMn3 Ni2 Mn2 O12 -Im–3
Rp (%) 1.89 2.44 1.94 2.26
as an example.
RF (%) 2.42 3.02 2.55 3.13
Impurities:
Molecules 2024, 29, 5488 4 of 17

Table 2. Structure parameters of RMn3 Ni2 Mn2 O12 (Pn–3; prepared at 1500 K) at room temperature
from synchrotron powder X-ray diffraction data.

R Nd Sm Gd Dy
a (Å) 7.35504(1) 7.34371(1) 7.33561(1) 7.32757(1)
V (Å3 ) 397.8824(2) 396.0468(5) 394.7375(5) 393.4419(4)
Biso (R) (Å2 ) 0.436(5) 0.532(5) 0.551(6) 0.661(5)
Biso (MnSQ ) (Å2 ) 0.541(9) 0.578(8) 0.560(9) 0.550(7)
0.82(2)Ni+ 0.834(17)Ni+ 0.82(2)Ni+ 0.831(16)Ni+
g(Ni1 /Mn1 )
0.18Mn 0.166Mn 0.18Mn 0.169Mn
Biso (Ni1 /Mn1 ) (Å2 ) 0.36(4) 0.42(4) 0.34(4) 0.38(3)
0.82Mn+ 0.834Mn+ 0.82Mn+ 0.831Mn+
g(Mn2 /Ni2 )
0.18Ni 0.166Ni 0.18Ni 0.169Ni
Biso (Mn2 /Ni2 ) (Å2 ) 0.38(4) 0.36(4) 0.45(4) 0.34(4)
x(O) 0.2576(5) 0.2576(5) 0.2576(6) 0.2574(5)
y(O) 0.42527(16) 0.42542(16) 0.42462(19) 0.42412(16)
z(O) 0.55854(15) 0.55767(14) 0.55771(17) 0.55632(14)
Biso (O) (Å2 ) 0.49(3) 0.62(3) 0.54(3) 0.60(3)
Rwp (%) 3.66 4.17 4.66 4.85
Rp (%) 2.40 2.78 2.87 3.32
Rp (%) 1.89 2.44 1.94 2.26
RF (%) 2.42 3.02 2.55 3.13
Impurities:
NiO (R–3m) 3.0 wt. % 2.8 wt. % 1.5 wt. % 1.8 wt. %
GdFeO3 -related – 0.5 wt. % 2.0 wt. % 1.7 wt. %
Space group Pn–3 (No. 201, setting 2); Z = 2. Fractional coordinates: R: 2a (0.25, 0.25, 0.25), MnSQ : 6d (0.25, 0.75,
0.75), Ni1 /Mn1 : 4b (0, 0, 0), Mn2 /Ni2 : 4c (0.5, 0.5, 0.5), and O: 24h (x, y, z). Occupation factors, g, of the R, MnSQ , O
sites are 1. Constraints on occupation factors: g(Mn1 ) = g(Ni2 ) = 1 − g(Ni1 ) and g(Mn2 ) = g(Ni1 ). GdFeO3 -related
impurities: for R = Sm, space group Pnma, a = 5.5165 Å, b = 7.6078 Å, c = 5.3470 Å; for R = Gd, space group P21 /n,
a = 5.2908 Å, b = 5.5452 Å, c = 7.5560 Å, β = 90.1356◦ ; for R = Dy, space group P21 /n, a = 5.2452 Å, b = 5.5423 Å,
c = 7.4960 Å, β = 90.2082◦ .

Table 3. Bond lengths (in Å), bond valence sums (BVS), and Ni–O–Mn bond angles (in deg) in
RMn3 Ni2 Mn2 O12 (Pn–3; prepared at 1500 K) at room temperature from synchrotron powder X-ray
diffraction data.

R Nd Sm Gd Dy
R–O × 12 (Å) 2.6105(11) 2.6015(11) 2.5959(13) 2.5824(11)
BVS(R3+ ) 3.16 3.00 2.86 2.74
MnSQ –O × 4 (Å) 1.9099(11) 1.9125(11) 1.9062(14) 1.9091(11)
MnSQ –O × 4 (Å) 2.7732(12) 2.7712(11) 2.7731(14) 2.7784(11)
BVS(Mn3+ ) 2.93 2.91 2.95 2.93
Ni1 /Mn1 –O × 6 (Å) 2.019(4) 2.014(3) 2.014(4) 2.009(3)
BVS(Ni2+ ) 2.24 2.27 2.27 2.30
Mn2 /Ni2 –O × 6 (Å) 1.915(4) 1.910(3) 1.910(4) 1.908(3)
BVS(Mn4+ ) 3.87 3.92 3.93 3.95
Ni1 –O–Mn2 138.38(6) 138.65(6) 138.38(8) 138.56(6)

Figure 3 shows lattice parameters as a function of the ionic radius [30] for RMn3 Ni2 Mn2 O12
samples with R = La [28], Nd, Sm, Gd, and Dy. Nearly linear behavior of the cubic lattice
parameter was observed. Figure 3 also shows R–O bond lengths and bond valence sum
(BVS) values [47] as a function of the ionic radius. The BVS values of Mn3+ , Mn4+ , and Ni2+
sites/cations were almost constant in all RMn3 Ni2 Mn2 O12 -Pn–3 compounds independent
of the R3+ cations and agreed well with the expected formal oxidation states. On the other
hand, the R–O bond length and the BVS values of the R sites changed monotonically and
noticeably, and they were dependent on the R3+ cations. In LaMn3 Ni2 Mn2 O12 [28], the
BVS value of the La site was +3.40, indicating that La3+ is highly overbonded (probably
for this reason, the BVS value of the La site was not mentioned and discussed in [28]).
In DyMn3 Ni2 Mn2 O12 , the BVS value of the Dy site was +2.72, indicating that Dy3+ is
Molecules 2024, 29, 5488 5 of 17

noticeably
Molecules 2024, 29, x FOR PEER REVIEW underbonded. The optimal BVS value of +3.0 is realized in SmMn Ni2 Mn2 O12 .
5 of3 17
Severe underbonding of R3+ could be a reason why RMn3 Ni2 Mn2 O12 with smaller R3+
cations (R = Er and Tm) could not be prepared.

0.6

Intensity (counts/106) 0.5 0.02

0.4

0.3

0.00
0.2
16.0 16.5 17.0 17.5

0.1

0.0

-0.1
6 16 26 36 46 56
2θ (deg): λ = 0.65298 Å

Figure
Figure 2. Experimental
2. Experimental (black
(black crosses),
crosses), calculated
calculated (red
(red line), line),
and and difference
difference (blue line (blue line at the bottom)
at the bottom)
room-temperature synchrotron X-ray powder diffraction patterns of NdMn
room-temperature synchrotron X-ray powder diffraction patterns of NdMn3 Ni2 Mn2 O3Ni 2 Mn 2 O 12 (in the Im–3(in the Im–3
12
modification, prepared at 1700 K) in a 2θ range of 6° and 59°. ◦ The tick
◦ marks show possible Bragg
modification, prepared at 1700 K) in a 2θ range of 6 and 59 . The tick marks show possible Bragg
reflection positions for the main phase and NiO impurity. Inset shows a zoomed part in a 2θ range
ofreflection positions
16° and 17.9° for the main
and emphasizes phase and
the absence of theNiO
(311)impurity.
reflection Inset
and theshows a zoomed
absence of B-site part in a 2θ range of
ordering.
16◦ and 17.9◦ and emphasizes the absence of the (311) reflection and the absence of B-site ordering.
Table 4. Structure parameters, bond lengths, and bond valence sums (BVSs) of RMn3Ni2Mn2O12 (Im–
3;Table 4. Structure
prepared at 1700 K)parameters, bond lengths,
at room temperature and bond valence
from synchrotron powdersums
X-ray(BVSs) of RMn
diffraction 3 Ni2 Mn2 O12 (Im–3;
data.
prepared at 1700 K) at room temperature from synchrotron powder X-ray diffraction data.
R Nd Sm
a (Å)R 7.35677(1)Nd 7.34621(1) Sm
V (Å3) 398.1629(5) 396.4512(5)
Biso(R)a (Å)
(Å2) 7.35677(1)
0.382(5) 0.285(5) 7.34621(1)
3) 2 398.1629(5)
Biso(Mn V SQ(Å) (Å ) 0.558(9) 0.413(8) 396.4512(5)
22 ) 0.382(5)
B
Biso(Ni/Mn)
iso (R) (Å
(Å ) 0.297(7) 0.228(6) 0.285(5)
x(O)SQ ) (Å2 )
Biso (Mn 0.558(9)
0.30930(16) 0.30505(15) 0.413(8)
Biso (Ni/Mn)
y(O) (Å2 ) 0.297(7)
0.17406(18) 0.17617(17) 0.228(6)
Biso(O)x(O)(Å )2 0.30930(16)
0.63(3) 0.10(2) 0.30505(15)
Rwpy(O)
(%) 0.17406(18)
4.46 5.56 0.17617(17)
(%) (Å2 )
Rp (O)
Biso 2.890.63(3) 3.59 0.10(2)
RRpwp(%)(%) 3.88 4.46 3.70 5.56
RR F (%)
p (%) 3.90 2.89 3.57 3.59
Impurities:
Rp (%) 3.88 3.70
NiOR(R–3m)
F (%) 2.9 wt. %3.90 4.1 wt. % 3.57
R–OImpurities:
× 12 (Å) 2.6110(12) 2.5879(11)
BVS(R
NiO 3+)
(R–3m) 3.16
2.9 wt. % 3.11 4.1 wt. %
MnSQ–O × 4 (Å) 1.8994(12) 1.9303(12)
R–O × 12 (Å) 2.6110(12) 2.5879(11)
MnSQ–O × 43+ (Å) 2.7781(13) 2.7767(12)
BVS(R3+ ) 3.16 3.11
BVS(Mn ) 3.00 2.78
Mn SQ –O
Ni/Mn–O × 6 (Å) × 4 (Å) 1.8994(12)
1.9711(4) 1.9572(4)
1.9303(12)
MnSQ –O
BVS(Ni 2+/Mn × 4+4)(Å) 2.7781(13)
2.91 3.02 2.7767(12)
BVS(Mn3+ )
Ni/Mn–O–Ni/Mn 137.85(7)3.00 139.56(7) 2.78
Ni/Mn–O × 6 (Å) 1.9711(4) 1.9572(4)
Space group Im–3 (No. 204); Z = 2. Fractional coordinates: R: 2a (0, 0, 0), MnSQ: 6b (0, 0.5, 0.5), Ni/Mn:
BVS(Ni 2+ /Mn4+ ) 2.91 g, of the R, MnSQ, O sites are3.02
8c (0.25, 0.25, 0.25), and O: 24g (x, y, 0). Occupation factors, 1. The
occupationNi/Mn–O–Ni/Mn
of the Ni/Mn site was fixed at 0.5Ni + 0.5Mn. 137.85(7) 139.56(7)
For BVS of Ni2+/Mn4+, an average R0 value
between R0(Ni2+Im–3
Space group ) = 1.654
(No.and R0(Mn
204); Z = 4+2.) =Fractional
1.753 was coordinates:
used [47]. R: 2a (0, 0, 0), MnSQ : 6b (0, 0.5, 0.5), Ni/Mn: 8c
(0.25, 0.25, 0.25), and O: 24g (x, y, 0). Occupation factors, g, of the R, MnSQ , O sites are 1. The occupation of the
Ni/Mn site was fixed at 0.5Ni + 0.5Mn. For BVS of Ni2+ /Mn4+ , an average R0 value between R0 (Ni2+ ) = 1.654 and
R0 (Mn4+ ) = 1.753 was used [47].
 LaMn3Ni2Mn2O12 [28], the BVS value of the La site was +3.40, indicating that La3+ is highly
overbonded (probably for this reason, the BVS value of the La site was not mentioned and
discussed in [28]). In DyMn3Ni2Mn2O12, the BVS value of the Dy site was +2.72, indicating
that Dy3+ is noticeably underbonded. The optimal BVS value of +3.0 is realized in
Molecules 2024, 29, 5488 SmMn3Ni2Mn2O12. Severe underbonding of R3+ could be a reason why RMn3Ni2Mn62O of1217
with smaller R3+ cations (R = Er and Tm) could not be prepared.

7.38
XRD
(a)
7.37 NPD

Lattice parameter, a (Å)

La
7.36
Im−3
7.35 Nd

7.34 Sm Pn−3

7.33 Gd

Dy
7.32
1.0 1.1 1.1 1.2 1.2
(b) 3.4
2.64

R3+ bond valence sum

R–O bond length (Å)

3.2
2.62

3.0

2.60
2.8

2.58 2.6
1.0 1.1 1.1 1.2 1.2
Ionic radius of R3+, rVIII (Å)
(a)The
Figure3.3.(a)
Figure Theroom-temperature
room-temperaturecubic cubiclattice
latticeparameter
parameter in in RMn
RMn33Ni Ni22Mn
Mn2O
2O (R(R= =
1212 LaLa [28],
[28], Nd,Nd,Sm,Sm,
Gd,and
Gd, andDy)Dy)asasa afunction
functionofofthe
theionic radiusRR3+3+(for
ionicradius (for the
the coordinationnumber
coordination number8 8asasionic
ionicradii
radiifor
forthe
the
coordination
coordinationnumber
numberXII XIIare
arenot
notavailable
availablefor smallRR3+3+cations
forsmall cations(R(R= =GdGdand
andDy)Dy)[30]).
[30]).NPD:
NPD:fromfrom
neutron
neutronpowder
powder diffraction.
diffraction. XRD: from X-ray
XRD: from X-raypowder
powderdiffraction.
diffraction.(b)(b)R–OR–O bond
bond length
length (the(the left-
left-hand
hand axis) and bond-valence sum for
3+ R 3+ (the right-hand axis) in RMn3Ni2Mn2O12 (R = La [28], Nd,
axis) and bond-valence sum for R (the right-hand axis) in RMn3 Ni2 Mn2 O12 (R = La [28], Nd, Sm,
Sm, Gd, and Dy) as a function of the ionic radius3+R3+.
Gd, and Dy) as a function of the ionic radius R .

Magnetic
Magneticproperties
properties of
of NdMn
NdMn33Ni
Ni22Mn
Mn22OO1212and
andSmMn
SmMn3Ni 2Mn2O12 compounds in two
3 Ni2 Mn2 O12 compounds in two
modifications
modifications(Pn–3
(Pn–3and
andIm–3)
Im–3)are
areshown
shownininFigures
Figures44and
and55(also
(alsomarked
markedby
bythe
thesynthesis
synthesis
temperatures between 1500 K and 1700 K). Temperature-dependent magnetic
temperatures between 1500 K and 1700 K). Temperature-dependent magnetic properties properties
were almost identical for the two modifications. Magnetic properties of GdMn3 Ni2 Mn2 O12
and DyMn3 Ni2 Mn2 O12 compounds (the Pn–3 modification) are shown in Figures 6 and 7;
they were dominated by large moments of Gd3+ and Dy3+ cations. Nevertheless, differential
dχ/dT versus T curves allowed the detection of one magnetic anomaly in GdMn3 Ni2 Mn2 O12
and two magnetic anomalies in DyMn3 Ni2 Mn2 O12 . At high temperatures, inverse magnetic
susceptibilities followed the Curie–Weiss law (see Figure 7 as an example), and we obtained
Curie–Weiss fitting parameters using the 10 kOe FCC curves in a temperature range of
200–350 K. The Curie–Weiss fitting parameters are summarized in Table 5. The experimen-
tal effective magnetic moments (µeff ) were close to the expected calculated values (µcalc ). It
is interesting that the Curie–Weiss temperatures (θ) were very small, suggesting that anti-
ferromagnetic and ferromagnetic interactions are of the same magnitude and nearly cancel
each other. In GdMn3 Ni2 Mn2 O12 and DyMn3 Ni2 Mn2 O12 compounds, the Curie–Weiss
temperatures were slightly positive, suggesting that ferromagnetic interactions are slightly
stronger. Unfortunately, no Curie–Weiss fits were reported for LaMn3 Ni2 Mn2 O12 [28] to
 in Table 5. The experimental effective magnetic moments (µeff) were close to the expected
calculated values (µcalc). It is interesting that the Curie–Weiss temperatures (θ) were very
small, suggesting that antiferromagnetic and ferromagnetic interactions are of the same
magnitude and nearly cancel each other. In GdMn3Ni2Mn2O12 and DyMn3Ni2Mn2O12 com-
Molecules 2024, 29, 5488 7 of 17
pounds, the Curie–Weiss temperatures were slightly positive, suggesting that ferromag-
netic interactions are slightly stronger. Unfortunately, no Curie–Weiss fits were reported
for LaMn3Ni2Mn2O12 [28] to compare with our data. It is possible that a similar “strange”
compare with our data. It is possible that a similar “strange” Curie–Weiss temperature
Curie–Weiss temperature was obtained; therefore, such data were not mentioned and dis-
was obtained; therefore, such data were not mentioned and discussed. In all R2 NiMnO6
cussed. In all R2NiMnO6 (R = La–Lu [10,16–19]), Tl2NiMnO6 [23], and In2NiMnO6 [20], pos-
(R = La–Lu [10,16–19]), Tl NiMnO6 [23], and In2 NiMnO6 [20], positive and large Curie–
itive and large Curie–Weiss2temperatures were found indicating that ferromagnetic inter-
Weiss temperatures were found indicating that ferromagnetic interactions are dominant.
actions are dominant. On the other hand, in Sc2NiMnO6 [22], a negative Curie–Weiss tem-
On the other hand, in Sc NiMnO6 [22], a negative Curie–Weiss temperature of about −60 K
perature of about −60 K 2was observed, indicating that antiferromagnetic interactions are
was observed, indicating that antiferromagnetic interactions are dominant. Therefore,
dominant. Therefore, there could be strong competition of different magnetic interactions
there could be strong competition of different magnetic interactions in RMn3 Ni2 Mn2 O12,
in RMn3Ni2Mn2O12, resulting in nearly zero Curie–Weiss temperatures.
resulting in nearly zero Curie–Weiss temperatures.

ZFC, 10 kOe, Nd-1500 K

1.5
1.6 FCC, 10 kOe, Nd-1500 K
ZFC, 10 kOe, Nd-1700 K
1.0
χ (emu× mol− 1× Oe− 1)

FCC, 10 kOe, Nd-1700 K

dχ T/dT

1.2
0.5

26 K
0.0
0.8
NdMn3Ni2Mn2O12
-0.5

0.4
-1.0
0 20 40 60 80

(a)
0.0
0 50 100 150 200 250 300 350

8 ZFC, 100 Oe, Nd-1500K

8 FCC, 100 Oe, Nd-1500 K
5
ZFC, 100 Oe, Nd-1700 K
χ (emu× mol− 1× Oe− 1)

dχ T/dT

FCC, 100 Oe, Nd-1700 K

2
6

-1

4
-4

-7
0 20 40 60 80
2

0
(b)
0 10 20 30 40 50 60 70 80

Temperature (K)

Figure4.4.(a)(a)
Figure ZFCZFC (filled
(filled symbols)
symbols) andand
FCCFCC (empty
(empty symbols)
symbols) dc magnetic
dc magnetic susceptibility
susceptibility curves curves
(χ =
M/H) of two of
(χ = M/H) modifications of NdMn
two modifications Ni2Mn32Ni
of 3NdMn O122 Mn
(the2 O
Pn–3 modification,
12 (the preparedprepared
Pn–3 modification, at 1500 K,atand
1500theK,
Im–3
and modification, preparedprepared
the Im–3 modification, at 1700 K)
at measured at H = 10atkOe.
1700 K) measured ThekOe.
H = 10 inset shows
The insetthe dχT/dT
shows versus
the dχT/dT
Tversus
curvesT(all). (b)(all).
curves ZFC(b) andZFC
FCC curves
and FCC of two modifications
curves of NdMn
of two modifications 3Ni2Mn2O12 measured at H =
of NdMn 3 Ni2 Mn2 O12 measured
100 Oe. The inset shows the FCC dχT/dT versus T curves.
at H = 100 Oe. The inset shows the FCC dχT/dT versus T curves.

Table 5. Temperatures of magnetic anomalies and parameters of the Curie–Weiss fits and M versus H
curves at T = 5 K for RMn3 Ni2 Mn2 O12 .

R T N (K) µeff (µB /f.u.) µcalc (µB /f.u.) θ (K) M S (µB /f.u.)
Nd (Pn–3) 26 11.08(2) 11.413 −1.7(1.0) 6.90
Nd (Im–3) 26 11.211(13) 11.413 −0.9(7) 7.04
Sm (Pn–3) 23 10.704(9) 10.966 −0.2(5) 4.70
Sm (Im–3) 23 10.842(9) 10.966 −2.7(5) 4.70
Gd (Pn–3) 22 13.383(7) 13.491 +8.4(3) 10.70
Dy (Pn–3) 10, 36 14.886(17) 15.178 +2.8(6) 11.36
The Curie–Weiss fits are performed between 200 and 350 K using the FCC χ −1 versus T data at 10 kOe. MS is the
magnetization value at T = 5 K and H = 70 kOe. µcalc is calculated using 3.5µB for Nd3+ , 1.5µB for Sm3+ , 8.0µB for
Gd3+ , 10.6µB for Dy3+ , 4.899µB for Mn3+ , 2.828µB for Ni2+ , and 3.873µB for Mn4+ . TN values were determined
from peaks on the 10 kOe FCC d(χT)/dT versus T or dχ/dT versus T curves.
Molecules 2024, 29, x FOR PEER REVIEW
Molecules 2024, 29, 5488 8 of 17

0.6

0.5
0.4
ZFC, 10 kOe, Sm-1500 K

χ (emu× mol− 1× Oe− 1)

dχ T/dT
FCC, 10 kOe, Sm-1500 K
0.4 23 K
ZFC, 10 kOe, Sm-1700 K
0.2 FCC, 10 kOe, Sm-1700 K
0.3

0.2 0.0
0 20 40 60 80

0.1

(a)
0.0
0 50 100 150 200 250 300 350
ZFC, 100 Oe, Sm-1500 K
FCC, 100 Oe, Sm-1500 K
ZFC, 100 Oe, Sm-1700 K
0.6
χ (emu× mol− 1× Oe− 1)

FCC, 100 Oe, Sm-1700 K

SmMn3Ni2Mn2O12

0.4

0.2

(b)
0.0
0 20 40 60 80 100

Temperature (K)

5. (a)
Figure 5.
Figure (a) ZFC
ZFC(filled symbols)
(filled and FCC
symbols) and (empty symbols)symbols)
FCC (empty dc magnetic
dcsusceptibility curves
magnetic susceptibility
(χ = M/H) of two modifications of SmMn3 Ni2 Mn2 O12 (the Pn–3 modification, prepared at 1500 K,
M/H) of two modifications of SmMn3Ni2Mn2O12 (the Pn–3 modification, prepared at 1500
and the Im–3 modification, prepared at 1700 K) measured at H = 10 kOe. The inset shows FCC
Im–3 modification, prepared at 1700 K) measured at H = 10 kOe. The inset shows FCC dχT
dχT/dT versus T curves. (b) ZFC and FCC curves of two modifications of SmMn3 Ni2 Mn2 O12
Tmeasured
curves. at(b)
H =ZFC and FCC curves of two modifications of SmMn3Ni2Mn2O12 measured
100 Oe.
Oe.
Isothermal magnetization curves (M versus H) of NdMn3Ni2Mn2O12 and SmMn3Ni2Mn2O12
compounds in two modifications (Pn–3 and Im–3) are shown in Figure 8. Again, M versus H
curves were almost identical for the two modifications.0.0
Small hysteresis near the origin was 0.00
found, but no saturation behavior was observed. M versus H curves of GdMn3 Ni2 Mn2 O12
and DyMn3 Ni2 Mn2 O12 compounds (Pn–3 modifications) -0.1 are shown in Figure 9; small
FCC, 100 Oe -0.02
hysteresis
2.0 near the origin was observed in GdMn3 Ni2 Mn2 O12 , while no hysteresis
FCC, 10 kOe was
dχ /dT

6 -0.2
detected in DyMn3 Ni2 Mn2 O12 . The M versus H curves of DyMn3 Ni2 Mn2 O12 were mainly
3+ -0.04
determined by properties of Dy cations and suggest the absence of any ferromagnetic-like
χ (emu× mol− 1× Oe− 1)

-0.3
contributions. Except for a very weak, extended hysteresis in SmMn3 Ni2 Mn2 O12 , its M versus
-0.06
H curve also suggests the4absence of any significant ferromagnetic-like contributions. On the
1.5 -0.4
22 K
other hand, M versus H curves of NdMn3 Ni2 Mn2 O12 and GdMn3 Ni2 Mn2 O12 were similar to
those of LaMn3 Ni2 Mn2 O12 [28] and suggest the presence
-0.5 of ferromagnetic-like contributions. -0.08
0 20 40 60 80 100

1.0 2 ZFC, 100 Oe

FCC, 100 Oe
0
0.5
0 10 20 30 40 50
GdMn3Ni2Mn2O12
ZFC, 10 kOe
(Pn−3; prepared at 1500 K)
 Figure 5. (a) ZFC (filled symbols) and FCC (empty symbols) dc magnetic susceptibility curves (χ =
M/H) of two modifications of SmMn3Ni2Mn2O12 (the Pn–3 modification, prepared at 1500 K, and the
Im–3 modification, prepared at 1700 K) measured at H = 10 kOe. The inset shows FCC dχT/dT versus
T curves. (b) ZFC and FCC curves of two modifications of SmMn3Ni2Mn2O12 measured at H = 100
Molecules 2024, 29, 5488 Oe. 9 of 17

0.0 0.00

-0.1
FCC, 100 Oe -0.02

dχ /dT
2.0 6 -0.2
FCC, 10 kOe

-0.04

χ (emu× mol− 1× Oe− 1)

-0.3

-0.06
1.5 4 -0.4
22 K
-0.5 -0.08
0 20 40 60 80 100

1.0 2 ZFC, 100 Oe

FCC, 100 Oe
0
0.5
0 10 20 30 40 50
GdMn3Ni2Mn2O12
ZFC, 10 kOe
(Pn−3; prepared at 1500 K)
FCC, 10 kOe
0.0
Molecules 2024, 29, x FOR PEER REVIEW 0 50 100 150 200 250 300 350 9 of
Temperature (K)
ZFC
Figure6.6.ZFC
Figure (filledsymbols)
(filled symbols)and and FCC
FCC (empty
(empty symbols)
symbols) dc dc magnetic
magneticsusceptibility
susceptibilitycurves
curves (χ =
first
M/H) inset
(χ =ofM/H)shows
GdMn of3Ni ZFC
GdMn
2Mn23O
and
Ni122 MnFCC
(the2 O curves
12 (the
Pn–3 of GdMn Ni
Pn–3 modification,
modification, Mn O
preparedprepared
3 2 2 12 measured
1500atK)Hmeasured
at measured
at 1500 K) =at100
H = Oe.
10 atTheThe
kOe. seco
inset
H = shows
10 kOe.theThe
FCC dχ/dT
first inset versus
shows T curves.
ZFC and FCC curves of GdMn3 Ni2 Mn2 O12 measured at
H = 100 Oe. The second inset shows the FCC dχ/dT versus T curves.

FCC, 100 Oe
ZFC, 10 kOe
1.4 0.00 FCC, 10 kOe
12
dχ /dT

1.2 10
χ (emu× mol− 1× Oe− 1)

-0.04

χ
TN1 = 36 K

−1
1.0
TN2 = 10 K μeff = 14.886(17)μB 8
-0.08
0 20 40 60 θ = +2.8(6) K (emu− 1× mol× Oe)
0.8 μcalc = 15.178μB
6
0.6
TN1 4
0.4
DyMn3Ni2Mn2O12
(Pn−3; prepared at 1500 K) 2
0.2 ZFC, 10 kOe
FCC, 10 kOe
0.0 0
0 50 100 150 200 250 300 350

Temperature (K)
ZFC(filled
Figure 7.7. ZFC
Figure (filled symbols)
symbols) and
and FCC
FCC(empty
(emptysymbols)
symbols) dc dc
magnetic susceptibility
magnetic curvescurves (
susceptibility
M/H) M/H)
(χ = of DyMn of 3Ni
DyMn
2Mn 3 2Ni
O212Mn 2 O12
(the Pn–3 Pn–3 modification,
(themodification, prepared
prepared at 1500at K)
1500 K) measured
measured at H =at10 kOe (
H = 10 kOe (the left-hand axis). The right-hand axis shows the FCC χ−1 versus T curve with
left-hand axis). The right-hand axis shows the FCC χ versus T curve with the Curie–Weiss fit (bl
−1
the Curie–Weiss fit (black line). The fitting parameters are given in the figure. The inset shows dχ/dT
line). The fitting parameters are given in the figure. The inset shows dχ/dT versus T curves.
versus T curves.

Table 5. Temperatures of magnetic anomalies and parameters of the Curie–Weiss fits and M ver
H curves at T = 5 K for RMn3Ni2Mn2O12.

R TN (K) μeff (μB/f.u.) μcalc (μB/f.u.) θ (K) MS (μB/f.u

Nd (Pn–3) 26 11.08(2) 11.413 −1.7(1.0) 6.90
Nd (Im–3) 26 11.211(13) 11.413 −0.9(7) 7.04
Sm (Pn–3) 23 10.704(9) 10.966 −0.2(5) 4.70
Sm (Im–3) 23 10.842(9) 10.966 −2.7(5) 4.70
Molecules 2024, 29, x FOR PEER REVIEW 10 of 17
Molecules 2024, 29, 5488 10 of 17

8
Nd-1500 K, 5 K
Nd-1700 K, 5 K
4 NdMn3Ni2Mn2O12

/ f.u.)
B
Magnetization (μ
0 (a) 3

0
-4
-1

-2

-3
-8 -4 0 4 8
-8
-80 -60 -40 -20 0 20 40 60 80
5

4 Sm-1500 K, 5 K

Sm-1700 K, 5 K
3
/ f.u.)

SmMn3Ni2Mn2O12
2
B

1
Magnetization (μ

0 (b) 1

-1

-2 0

-3

-4
-1
-8 -4 0 4 8
-5
-80 -60 -40 -20 0 20 40 60 80
Magnetic Field (kOe)

MM
Figure8. 8.
Figure versus
versus H curves
H curves of two
of two modifications
modifications of RMn
of RMn 3 Ni22OMn
3Ni2Mn 2 O12Pn–3
12 (the Pn–3 modification,
(the modification, pre-
prepared
pared at 1500at K,
1500
andK,the
andIm–3 Im–3 modification,
the modification, prepared
prepared at 1700atK)1700 K) measured
measured KT
at T = 5 at = 5(a)
with KR with
=
Nd
(a)and
R =(b)
NdRand= Sm.
(b)The
R = insets show
Sm. The zoomed
insets show parts
zoomednearparts
the origin.
near the origin.

Specificheat
Specific heat data
data for twofor two modifications
modifications of SmMnof SmMn
3Ni2Mn 3 2Ni
O12 2 Mn 2 Omeasured
were 12 were measured
(Figure
(Figure
10b), and 10b),
almostandno almost
difference no was
difference
observed.wasSpecific
observed.
heat Specific
data for the heatPn–3 for the Pn–3
datamodification
ofmodification
other compounds of other
(R compounds
= Nd, Gd, and (RDy)
= Nd,areGd, and in
shown Dy) are shown
Figure in Figure
10. Specific heat10. Specific
measure-
heat measurements confirmed one clear magnetic transition
ments confirmed one clear magnetic transition in the samples with R = Nd, Sm, and in the samples with R =Gd Nd,
Sm, and Gd and two clear magnetic transitions in the sample
and two clear magnetic transitions in the sample with R = Dy in agreement with the χ with R = Dy in agreement
with the
versus χ versus T measurements.
T measurements. In the case of LaMn In the3Ni
case
2Mnof2OLaMn 3 Ni
12 [28], 2 Mn2 Oheat
specific 12 [28], specific heat
measurements
measurements
could detect twocould detecttransitions
magnetic two magneticat 34transitions
K and 46 K, at 34 K and
where the 46transition
K, where at the46transition
K was
at 46 K was assigned to a long-range ordering of Mn 3+ cations at the square-planar A′
assigned to a long-range ordering of Mn cations at the square-planar A′ sites, and the
3+

sites, andatthe
transition 34 transition
K was assignedat 34 K towas assigned ordering
a long-range to a long-range
of Ni2+ ordering Ni2+ and tem-
and Mn4+.ofTransition Mn4+ .
Transitionfound
peratures temperatures
in R = Nd, foundSm,inand
R =Gd Nd,were
Sm, and Gd were
noticeably noticeably
smaller than smaller
those ofthanR =those
La.
of R = La. Therefore, it is possible that the size of R 3+ cations plays an important role
Therefore, it is possible that the size of R3+ cations plays an important role and can move
and
the can move
systems into the systems
different groundinto states.
different ground
Another states. Another
possibility is that the possibility
degree ofisNithat the
2+ and
degree of Ni 2+ and Mn4+ cation ordering plays an important role and determines magnetic
Mn4+ cation ordering plays an important role and determines magnetic transition temper-
transition temperatures.
atures.
Molecules
Molecules 2024,
2024, 29,
29, x
x FOR
FOR PEER
PEER REVIEW
REVIEW 11 of 17
11 of 17
Molecules 2024, 29, 5488 11 of 17

12
12
Gd-1500
Gd-1500 K, K, 55K K
8
8 Dy-1500 K,
Dy-1500 K, 5 K 5 K
RMn
RMn33Ni
Ni22Mn
Mn22O

f.u.)
O12

(μ BB // f.u.)
12
(Pn−3;
(Pn−3; prepared at
prepared at 1500
1500 K)
K)
4
4

Magnetization (μ
0
0
Magnetization
4
4

2
2
-4
-4
0
0

-8
-8 -2
-2

-4
-4

-12
-8 -4 0 4 8
-12
-8 -4 0 4 8

-80
-80 -60
-60 -40
-40 -20
-20 0
0 20
20 40
40 60
60 80
80
Magnetic
Magnetic Field
Field (kOe)
(kOe)
Figure
Figure9.
Figure 9.9.M
MMversus
versusH
versus HHcurves
curves of
curves of GdMn
of GdMn333NiNi222Mn
Ni Mn22O
Mn 2O
O 1212and
12 andDyMn
and DyMn
DyMn 33Ni 22Mn
3 Ni
Ni 22O
2 Mn
Mn O12
O212
12 (the Pn–3
(the
(the Pn–3 modification,
Pn–3 modification,
modification,
prepared
prepared at 1500
at K)
1500 measured
K) measured at T
at =
T 5
= K.
5 The
K. The inset
insetshows
showszoomed
zoomed parts
partsnear
near
prepared at 1500 K) measured at T = 5 K. The inset shows zoomed parts near the origin. the origin.
the origin.

26
26 K
K 0
0 Oe,
Oe, Nd-1500K
Nd-1500K
0
0 Oe,
Oe, Sm-1500K
Sm-1500K
2.0
2.0 2.0
2.0 90
90 kOe,
kOe, Sm-1500K
Sm-1500K
90
90 kOe,
kOe, Nd-1500K
Nd-1500K 0 Oe,
0 Oe, Sm-1700K
Sm-1700K
mol−−11))

90
90 kOe,
kOe, Sm-1700K
Sm-1700K
1.5 1.5
(J× KK−−22×× mol

1.5 1.5
2.0
2.0
23
23 K
K
1.0
1.0
1.5
1.5 1.0
1.0
CCpp//TT(J×

1.0
1.0

0.5 NdMn 0.5

0.5 0.5 NdMn33Ni
Ni22Mn
Mn22O
O12 0.5
0.5
(Pn−3;
(Pn−3; prepared
prepared at
12
at 1500
1500 K)
K)
(a)
(a)
0.0
0.0
0 50 100 150 200 250 SmMn33Ni
SmMn Ni22Mn
Mn22O
O12
12
(b)
(b)
0.0
0.0
0 50 100 150 200 250 0.0
0.0
0
0 20
20 40
40 60
60 80
80 100
100 0
0 20
20 40
40 60
60 80
80 100
100
0
0 Oe,
Oe, Gd
Gd 10
10 K
K 0
0 Oe,
Oe, Dy
Dy
2.0
2.0 2.0
2.0
90 90
90 kOe,
kOe, Dy
Dy
90 kOe,
kOe, Gd
mol−−11))

Gd
(J× KK−−22×× mol

1.5
1.5 1.5
1.5

22
22 K
K 36
36 K
K
1.0
1.0 1.0
1.0
CCpp//TT(J×

0.5
0.5 0.5
0.5
GdMn
GdMn33Ni
Ni22Mn
Mn22O
O12
12
DyMn
DyMn33Ni
Ni22Mn
Mn22O
O12
(Pn−3; prepared
(Pn−3; prepared at
at 1500
1500 K)
K) (c)
(c) (Pn−3; prepared
(Pn−3; prepared at
12
at 1500
1500 K)
K) (d)
(d)
0.0
0.0 0.0
0.0
00 20
20 40
40 60
60 80
80 100
100 0
0 20
20 40
40 60
60 80
80 100
100
Temperature
Temperature (K)
(K)
Figure
Figure
Figure CppC/T
10.10.
10. C /Tp /T versus
versus
versus T T curves
T curves
curves of of RMn
of RMn
RMn 33Ni Ni222O
Ni223Mn
Mn Mn
O O12 measured
measured
12 2
12 measured at H ==at00 H
at H = 0 (black
(black
(black curves)
curves)
curves) and
and 9090and
kOe90(red
kOe kOe
(red
(red
curves) curves)
for (a) for
R = (a)
Nd R =
(theNd (the
Pn–3 Pn–3 modification),
modification), (b) R = (b)
Sm R =
(theSm (the
Pn–3 Pn–3 modification
modification
curves) for (a) R = Nd (the Pn–3 modification), (b) R = Sm (the Pn–3 modification and the Im–3 mod- and theand
Im–3the Im–3
mod-
ification (blue
modification
ification and
and brown
(blue (blue curves)),
and brown
brown (c)
(c) R
curves)),
curves)), == Gd
R(c) R = (the
Gd Gd (the
(the Pn–3
Pn–3 modification),
Pn–3 modification),
modification), and (d)
andand R
R ==R Dy
(d)(d) = Dy
Dy (the
(thePn–3
(the Pn–3
Pn–3
modification). Arrows
modification).Arrows
modification). show
Arrowsshow magnetic
showmagnetic transition
magnetictransition temperatures.
transition temperatures. Data
temperatures. Data below below 100
below 100 K are
100KKare shown;
areshown; inset
shown;inset
inseton
on panel
panel(a)(a)
onpanel shows
(a)shows
showsfull full data
dataupup
fulldata uptoto 270
to270
270KK(at(at
K HH
(at H= ==0 00Oe).
Oe).
Oe).
Molecules 2024, 29, x FOR PEER REVIEW 12 of 17
Molecules 2024, 29, 5488 12 of 17

To get a deeper understanding of magnetic behavior, we measured ac magnetic sus-

To get
ceptibility a deeper
curves of theunderstanding of magnetic
Pn–3 modification of NdMn behavior,
3Ni2Mn2O we measured
12 as an exampleac magnetic
(Figure 11).sus-
ceptibility
Small curves
frequency of the Pn–3 in
dependence modification
the χ″ peakofintensities
NdMn3 Niwas 2 Mnobserved;
2 O12 as an however,
example (Figure
peak po- 11).
Small in
sitions frequency dependence
temperature were almost χ′′ peak intensities
in theindependent was observed;
of frequency, however,
suggesting peak posi-
that there are
notions in temperature
spin-glass-like were almost
contributions. Noindependent
dependenceof onfrequency,
the applied suggesting that
Hac field of there
0.05, 0.5,are
andno
spin-glass-like contributions. No dependence on the applied
5 Oe (inset of Figure 11) was also observed on both the χ′ versus H field of 0.05, 0.5,
ac T and the χ″ versus Tand 5 Oe
(inset of
curves. Figure
Peaks on 11)
thewas also observed
χ′ versus T curveson both
were the χ′ versus
observed near 14T and the χ′′peaks
K, while versusonTthe curves.
χ″
PeaksTon ′
the χwere
versus T curves were ′′
versus curves observed near 9 K.observed near 14 K,were
Both temperatures whiledifferent
peaks on the peak
from χ versus
po-
T curves
sitions on were
the dcobserved near 9 K.
dχT/dT versus Both temperatures
T curves, but peaks on were
the different
χ′ versusfrom peakbasically
T curves positions
on the dc dχT/dT versus T curves, but peaks on the χ ′ versus T curves basically matched
matched with the peak on the ZFC dc χ versus T curve measured at a small magnetic field
ofwith the Oe
H = 100 peak on the
(Figure ZFC dc χ versus T curve measured at a small magnetic field of
4b).
H = 100 Oe (Figure 4b).

3.00
3 0.05 Oe, 300 Hz
0.5 Oe, 300 Hz
(a)
5 Oe, 300 Hz

2.50 2
χ ’ (emu× mol− 1× Oe− 1)

2.00 1

1.50 f=
0
2 Hz 0 20 40 60
1.00 7 Hz
110 Hz Hac = 5 Oe
0.50 300 Hz Hdc = 0 Oe
500 Hz
0.00
0 20 40 60 80

(b)
0.08
NdMn3Ni2Mn2O12
χ ’ ’ (emu× mol− 1× Oe− 1)

(Pn−3; prepared at 1500 K)

0.06

0.04

0.02
2 Hz
7 Hz
0.00 110 Hz
300 Hz
500 Hz
-0.02
0 20 40 60 80
Temperature (K)
Figure11.
Figure (a)(a)
11. Real
Real χ′ versus
χ′ versus T and
T and (b) (b) imaginary
imaginary χ′′ versus
χ″ versus T curves
T curves of NdMn
of NdMn 3 Ni
3Ni2Mn 2O2 Mn 2 O12
12 (the
(the
Pn–3
Pn–3 modification) at different frequencies (f ). Inset shows the χ ′ versus T curves at different H
modification) at different frequencies (f). Inset shows the χ′ versus T curves at different Hac (Hac =ac
(Hac0.5,
0.05, = 0.05,
and 0.5, and
5 Oe) and5 Oe)
one and one frequency
frequency (f = 300 Hz).
(f = 300 Hz).

Consideringthe
Considering thepresence
presenceofofspin-induced
spin-inducedferroelectric
ferroelectricproperties
propertiesin
inIn
In2NiMnO
2 NiMnO [21]
6 6[21]
and complex magnetodielectric effects in
and complex magnetodielectric effects in Sc2NiMnOSc2 NiMnO 6 we checked the presence or ab-or
[22],
6 [22],
we checked the presence
absence of magnetodielectric effects in such
sence of magnetodielectric effects in such RMn3Ni2MnRMn Ni
3 2O2 Mn 2 O12 perovskites
12 perovskites selectingselecting
the Pn–3 the
Pn–3 modification of NdMn
modification of NdMn3Ni2Mn Ni
3 2O Mn
2 12 asO
2 an as an example (Figure 12). However,
12 example (Figure 12). However, no dielectric no dielectric
anomalies were observed near the magnetic transition temperature. The dielectric constant
Molecules 2024, 29, x FOR PEER REVIEW 13 of 17

Molecules 2024, 29, 5488 13 of 17

anomalies were observed near the magnetic transition temperature. The dielectric con-
stant showed a sharp increase above about 50 K (at 100 Hz) with characteristic frequency-
dependent
showed apeaks
sharponincrease
the loss above
tangent. These
about 50features correspond
K (at 100 Hz) withtocharacteristic
increased conductivity
frequency-
and Maxwell–Wagner contributions. Therefore, NdMn 3 Ni 2Mn2 O12 perovskiteconductivity
dependent peaks on the loss tangent. These features correspond to increased does not
show magnetodielectric contributions.
and Maxwell–Wagner effects and magnetic-transition-induced
Therefore, NdMn3 Ni2 Mn2 Oferroelectric
12 perovskitepolariza-
does not
tion.
show magnetodielectric effects and magnetic-transition-induced ferroelectric polarization.

100 Hz
301 Hz
90
903 Hz
2.71 kHz
Dielectric constant

8.16 kHz
24.5 kHz
70 73.7 kHz
221 kHz
665 kHz

50 (a)

NdMn3Ni2Mn2O12
(Pn−3; prepared at 1500 K)
30
0 50 100 150 200

1.4 10
103/Tmax

180 Tmax
1.2
Tmax (K)

1.0 130
Loss tangent

6
0.8
80 4
0.6 2 4 6 100 Hz
log(f) 301 Hz
903 Hz
0.4 2.71 kHz
8.16 kHz
24.5 kHz
0.2 (b) 73.7 kHz
221 kHz
665 kHz
0.0
0 50 100 150 200
Temperature (K)
Figure12.12.
Figure Temperature
Temperature dependence
dependence of dielectric
of (a) (a) dielectric constant
constant and and (b) tangent
(b) loss loss tangent at different
at different fre-
frequencies
quencies (f : indicated
(f: indicated onfigure)
on the the figure)
in NdMnin NdMn
3Ni2Mn 3 Ni
2O Mn
2 12 2 O12
(the Pn–3 Pn–3 modification)
(themodification) H =Inset
at H = 0atOe. 0 Oe.
Inset frequency
shows shows frequency dependence
dependence of peakof peak positions
positions on loss on loss tangent
tangent as Tmax as Tmaxlog(f)
versus versus log(fcircles
(black ) (black
with line)
circles andline)
with 1000/Tand versusmax
1000/T
max log(f) (redlog(f
versus squares with
) (red line).with line).
squares

InInthe
thecase
caseofofdouble
doubleperovskites
perovskitesRR2NiMnO
2 NiMnO 6 with
6 with ferromagneticground
ferromagnetic groundstates,
states,the
the
degreeofofordering
orderingofofNi
Ni 2+ and Mn 4+ cations has significant effects on magnetic properties,
degree 2+ and Mn4+ cations has significant effects on magnetic properties,
especiallyononthe
especially thesaturation
saturationmagnetization
magnetizationon onMMversus
versusHHcurves,
curves,where
wherea afull
fullordering
orderingofof
Ni 2+ and Mn4+ cations should give the magnetization of about 5µ /f.u. [10]. Deviations
Ni and Mn cations should give the magnetization of about 5µB/f.u. [10]. Deviations of
2+ 4+ B
of saturation
the the saturation magnetization
magnetization fromfrom 5µBcan
5µB/f.u. /f.u.give
caninformation
give information
about about the degree
the degree of Ni2+of
Ni2+ and Mn4+ disordering. On the other hand, we found that the saturation magnetiza-
tion on the M versus H curves of RMn3 Ni2 Mn2 O12 (and other magnetic properties) was
Molecules 2024, 29, 5488 14 of 17

almost independent of the degree of Ni2+ and Mn4+ disordering. This fact suggests that
different magnetic ground states could be realized in all RMn3 Ni2 Mn2 O12 in comparison
with R2 NiMnO6 , and magnetic structures of RMn3 Ni2 Mn2 O12 should be studied with
neutron diffraction in future works. Magnetic transition temperatures and properties
did not show any clear systematic trends as a function of the ionic radius of R3+ cations
in RMn3 Ni2 Mn2 O12 . On the other hand, in R2 NiMnO6 perovskites, magnetic transition
temperatures show a clear and sharp decrease with decreasing the ionic radius of R3+
cations [18,19,25,28].
Effects of the synthesis conditions on the degree of B-site cation ordering were ob-
served before, for example, in La2 NiMnO6 [9], Tl2 NiMnO6 [23], and CaCu3 Fe2 Os2 O12 [36],
where higher-temperature annealing (at high pressures) usually results in B-site cation
disordering. Our results on RMn3 Ni2 Mn2 O12 are consistent with the tendencies observed
in the literature.

3. Materials and Methods

RMn3 Ni2 Mn2 O12 samples with R = Nd, Sm, Gd, and Dy were prepared from stoichio-
metric mixtures of R2 O3 (Rare Metallic Co., Tokyo, Japan, 99.9%), Mn2 O3 , single-phase
and stoichiometric MnO2 (Alfa Aesar, Waltham, MA, USA, 99.9%), and NiO (Rare Metallic
Co., Tokyo, Japan, 99.9%). Single-phase Mn2 O3 was prepared from a commercial MnO2
chemical (Rare Metallic Co., Tokyo, Japan, 99.99%) by annealing in air at 923 K for 24 h. The
synthesis was performed at about 6 GPa and at about 1500 K for 2 h in sealed Au capsules
and at about 1700 K for 2 h in sealed Pt capsules using a belt-type HP instrument. After
annealing at high temperatures, the samples were cooled down to room temperature by
turning off the heating current, and the pressure was slowly released. We note that we
also tried to prepare RMn3 Ni2 Mn2 O12 samples with smaller R3+ cations, such as R = Er
and Tm (at 6 GPa and 1500 K). However, the samples contained a lot of impurities. The
R = Er sample (with a = 7.3189 Å) had ErMn2 O5 (9.5 wt. %), NiO (9.2 wt. %), and a
corundum-structure impurity (2.4 wt. %). The R = Tm sample (with a = 7.3190 Å) had
TmMn2 O5 (15.7 wt. %), NiO (8.2 wt. %), and a corundum-structure impurity (6.1 wt. %).
The presence of large amounts of impurities suggests that the chemical compositions of the
main phases significantly shifted from the target composition.
X-ray powder diffraction (XRPD) data were collected at room temperature on a Mini-
Flex600 diffractometer (Rigaku, Tokyo, Japan) using CuKα radiation (2θ range of 8–100◦ ,
a step width of 0.02◦ , and scan speed of 2◦ /min). Room-temperature synchrotron XRPD
data were measured on the BL15XU beamline (the former NIMS beamline) of SPring-8
(Hyogo, Japan) [48] between 2.04◦ and 60.23◦ at 0.003◦ intervals in 2θ with the wavelength
of λ = 0.65298 Å. The samples were placed into open Lindemann glass capillary tubes
(inner diameter: 0.1 mm), which were rotated during measurements. The Rietveld analysis
of all XRPD data was performed using the RIETAN-2000 program [49].
Magnetic measurements were performed on SQUID magnetometers (Quantum Design
MPMS-7T and MPMS3, San Diego, CA, USA) between 2 and 300 K (or 400 K) in applied
fields of 100 Oe and 10 kOe under both zero-field-cooled (ZFC) and field-cooled on cooling
(FCC) conditions. Magnetic-field dependence was measured at different temperatures
between −70 and 70 kOe. Frequency-dependent alternating current (ac) susceptibility
measurements were performed on cooling with an MPMS-1T instrument Quantum Design,
San Diego, CA, USA) at different frequencies (f ), different applied oscillating magnetic
fields (Hac ), and zero static dc field (Hdc = 0 Oe).
Specific heat, Cp , was measured on cooling from 270 K to 2 K at zero magnetic field
and from 100 K to 2 K at a magnetic field of 90 kOe by a pulse relaxation method using a
commercial calorimeter (Quantum Design PPMS, San Diego, CA, USA). All magnetic and
specific heat measurements were performed using pieces of pellets.
Dielectric properties were measured using an Alpha-A High-Performance Frequency
Analyzer (NOVOCONTROL Technologies, Montabaur, Germany) on cooling and heating
in a temperature range between 3 K and 300 K and a frequency range from 100 Hz to
Molecules 2024, 29, 5488 15 of 17

665 kHz at a zero magnetic field. The cooling–heating rate was 2 K/min between 70 K and
300 K and 0.5 K/min between 3 K and 70 K.
Scanning electron microscopy (SEM) images were obtained on a Miniscope TM3000
operating at 15 kV (Hitachi, Tokyo, Japan).

4. Conclusions
A-site-ordered quadruple perovskites, RMn3 Ni2 Mn2 O12 with R = Nd, Sm, Gd, and
Dy, were synthesized by a high-pressure, high-temperature method at about 6 GPa in
two modifications. Annealing at a lower temperature of about 1500 K favors a (partial)
B-site ordering, while annealing at a higher temperature of about 1700 K gives a disordered
arrangement of Ni2+ and Mn4+ cations. The B-site-ordered structure has space group Pn–3,
while the B-site-disordered structure has space group Im–3. However, magnetic properties
were nearly identical for the Pn–3 and Im–3 modifications in comparison with ferromagnetic
double perovskites R2 NiMnO6 . RMn3 Ni2 Mn2 O12 samples show one magnetic transition
at 26 K for R = Nd, 23 K for R = Sm, and 22 K for R = Gd, as well as two magnetic
transitions at 10 K and 36 K for R = Dy. Curie–Weiss temperatures were close to zero in all
compounds, suggesting that antiferromagnetic and ferromagnetic interactions are of the
same magnitude.

Author Contributions: Conceptualization, A.A.B.; methodology, A.A.B.; validation, A.A.B.; formal

analysis, A.A.B.; investigation, A.A.B., R.L., M.T. and K.Y.; resources, K.Y.; data curation, A.A.B.;
writing—original draft preparation, A.A.B.; writing—review and editing, A.A.B.; supervision, A.A.B.
and K.Y.; project administration, A.A.B.; funding acquisition, K.Y. All authors have read and agreed
to the published version of the manuscript.
Funding: This work was partially supported by a Grant-in-Aid for Scientific Research (No. JP22H04601)
from the Japan Society for the Promotion of Science and the Kazuchika Okura Memorial Foundation
(No. 2022-11).
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: The raw data supporting the conclusions of this article will be made
available by the author upon request.
Acknowledgments: The synchrotron radiation experiments were conducted at the former NIMS
beamline (BL15XU) of SPring-8 with the approval of the former NIMS Synchrotron X-ray Station
(proposal numbers: 2019A4501, 2019B4500, and 2020A4501). We thank Y. Katsuya for his help at
SPring-8. MANA was supported by the World Premier International Research Center Initiative (WPI),
MEXT, Japan.
Conflicts of Interest: The authors declare no conflicts of interest.

References
1. Vasala, S.; Karppinen, M. A2 B′ B′′ O6 perovskites: A review. Prog. Solid State Chem. 2015, 43, 1–36. [CrossRef]
2. Vasil’ev, A.N.; Volkova, O.S. New functional materials AC3 B4 O12 (Review). Low Temp. Phys. 2007, 33, 895–914. [CrossRef]
3. Long, Y. A-site ordered quadruple perovskite oxides AA′ 3 B4 O12 . Chin. Phys. B 2016, 25, 078108. [CrossRef]
4. Yamada, I. Novel catalytic properties of quadruple perovskites. Sci. Technol. Adv. Mater. 2017, 18, 541–548. [CrossRef]
5. Belik, A.A.; Johnson, R.D.; Khalyavin, D.D. The rich physics of A-site-ordered quadruple perovskite manganites AMn7 O12 .
Dalton Trans. 2021, 50, 15458–15472. [CrossRef]
6. Ding, J.; Zhu, X.H. Research progress on quadruple perovskite oxides. J. Mater. Chem. C 2024, 12, 9510–9561. [CrossRef]
7. Solana-Madruga, E.; Arevalo-Lopez, A.M. High-pressure A-site manganites: Structures and magnetic properties. J. Solid State
Chem. 2022, 315, 123470. [CrossRef]
8. Weihe, H.; Gudel, H.U. Quantitative interpretation of the Goodenough-Kanamori rules: A critical analysis. Inorg. Chem. 1997,
36, 3632–3639. [CrossRef]
9. Dass, R.I.; Yan, J.-Q.; Goodenough, J.B. Oxygen stoichiometry, ferromagnetism, and transport properties of La2-x NiMnO6-δ . Phys.
Rev. B 2003, 68, 064415. [CrossRef]
10. Rogado, N.S.; Li, J.; Sleight, A.W.; Subramanian, M.A. Magnetocapacitance and magnetoresiatance near room temperature in a
ferromagnetic semiconductor: La2 NiMnO6 . Adv. Mater. 2005, 17, 2225–2227. [CrossRef]
Molecules 2024, 29, 5488 16 of 17

11. Kobayashi, Y.; Shiozawa, M.; Sato, K.; Abe, K.; Asai, K. Crystal structure, magnetism, and dielectric properties of
La1-x Bix Ni0.5 Mn0.5 O3 . J. Phys. Soc. Jpn. 2008, 77, 084701. [CrossRef]
12. Choudhury, D.; Mandal, P.; Mathieu, R.; Hazarika, A.; Rajan, S.; Sundaresan, A.; Waghmare, U.V.; Knut, R.; Karis, O.; Nordblad,
P.; et al. Near-room-temperature colossal magnetodielectricity and multiglass properties in partially disordered La2 NiMnO6 .
Phys. Rev. Lett. 2012, 108, 127201. [CrossRef]
13. Guo, Y.Q.; Shi, L.; Zhou, S.M.; Zhao, J.I.; Liu, W.J. Near room-temperature magnetoresistance effect in double perovskite
La2 NiMnO6 . Appl. Phys. Lett. 2013, 102, 222401. [CrossRef]
14. Vasiliev, A.N.; Volkova, O.S.; Lobanovskii, L.S.; Troyanchuk, I.O.; Hu, Z.; Tjeng, L.H.; Khomskii, D.I.; Lin, H.J.; Chen, C.T.; Tristan,
N.; et al. Valence states and metamagnetic phase transition in partially B-site-disordered perovskite EuMn0.5 Co0.5 O3 . Phys. Rev. B
2008, 77, 104442. [CrossRef]
15. Sánchez-Benítez, J.; Martínez-Lope, M.J.; Alonso, J.A.; García-Muñoz, J.L. Magnetic and structural features of the NdNi1-x Mnx O3
perovskite series investigated by neutron diffraction. J. Phys. Condens. Matter 2011, 23, 226001. [CrossRef] [PubMed]
16. Retuerto, M.; Muñoz, Á.; Martínez-Lope, M.J.; Alonso, J.A.; Mompeán, F.J.; Fernández-Díaz, M.T.; Sánchez-Benítez, J. Magnetic
interactions in the double perovskites R2 NiMnO6 (R = Tb, Ho, Er, Tm) investigated by neutron diffraction. Inorg. Chem. 2015,
54, 10890–10900. [CrossRef]
17. Booth, R.J.; Fillman, R.; Whitaker, H.; Nag, A.; Tiwari, R.M.; Ramanujachary, K.V.; Gopalakrishnan, J.; Lofland, S.E. An
investigation of structural, magnetic and dielectric properties of R2 NiMnO6 (R = rare earth, Y). Mater. Res. Bull. 2009,
44, 1559–1564. [CrossRef]
18. Nasir, M.; Kumar, S.; Patra, N.; Bhattacharya, D.; Jha, S.N.; Basaula, D.R.; Bhatt, S.; Khan, M.; Liu, S.-W.; Biring, S.; et al. Role of
antisite disorder, rare-earth size, and superexchange angle on band gap, Curie temperature, and magnetization of R2 NiMnO6
double perovskites. ACS Appl. Electron. Mater. 2019, 1, 141–153. [CrossRef]
19. Asai, K.; Fujiyoshi, K.; Nishimori, N.; Satoh, Y.; Kobayashi, Y.; Mizoguchi, M. Magnetic properties of REMe0.5 Mn0.5 O3 (RE = rare
earth element, Me = Ni, Co). J. Phys. Soc. Jpn. 1998, 67, 4218–4228. [CrossRef]
20. Yi, W.; Liang, Q.F.; Matsushita, Y.; Tanaka, M.; Belik, A.A. High-pressure synthesis, crystal structure, and properties of In2 NiMnO6
with antiferromagnetic order and field-induced phase transition. Inorg. Chem. 2013, 52, 14108–14115. [CrossRef]
21. Terada, N.; Khalyavin, D.D.; Manuel, P.; Yi, W.; Suzuki, H.S.; Tsujii, N.; Imanaka, Y.; Belik, A.A. Ferroelectricity induced by
ferriaxial crystal rotation and spin helicity in a B-site-ordered double-perovskite multiferroic In2 NiMnO6 . Phys. Rev. B 2015,
91, 104413. [CrossRef]
22. Yi, W.; Princep, A.J.; Guo, Y.F.; Johnson, R.D.; Khalyavin, D.D.; Manuel, P.; Senyshyn, A.; Presniakov, I.A.; Sobolev, A.V.;
Matsushita, Y.; et al. Sc2 NiMnO6 : A double-perovskite with a magnetodielectric response driven by multiple magnetic orders.
Inorg. Chem. 2015, 54, 8012–8021. [CrossRef] [PubMed]
23. Ding, L.; Khalyavin, D.D.; Manuel, P.; Blake, J.; Orlandi, F.; Yi, W.; Belik, A.A. Colossal magnetoresistance in the insulating
ferromagnetic double perovskites Tl2 NiMnO6 : A neutron diffraction study. Acta Mater. 2019, 173, 20–26. [CrossRef]
24. Sobolev, A.V.; Glazkova, I.S.; Akulenko, A.A.; Sergueev, I.; Chumakov, A.I.; Yi, W.; Belik, A.A.; Presniakov, I.A. 61 Ni nuclear
forward scattering study of magnetic hyperfine interactions in double perovskites A2 NiMnO6 (A = Sc, In, Tl). J. Phys. Chem. 2019,
123, 23628–23634. [CrossRef]
25. Terada, N.; Colin, C.V.; Qureshi, N.; Hansen, T.; Matsubayashi, K.; Uwatoko, Y.; Belik, A.A. Pressure-induced incommensurate
antiferromagnetic order in a ferromagnetic B-site ordered double-perovskite Lu2 NiMnO6 . Phys. Rev. B 2020, 102, 094412.
[CrossRef]
26. Manna, K.; Bera, A.K.; Jain, M.; Elizabeth, S.; Yusuf, S.M.; Anil Kumar, P.S. Structural-modulation-driven spin canting and
reentrant glassy magnetic phase in ferromagnetic Lu2 MnNiO6 . Phys. Rev. B 2015, 91, 224420. [CrossRef]
27. Dieguez, O.; Iniguez, J. Multiferroic Bi2 NiMnO6 thin films: A computational prediction. Phys. Rev. B 2017, 95, 085129. [CrossRef]
28. Yin, Y.Y.; Liu, M.; Dai, J.H.; Wang, X.; Zhou, L.; Cao, H.; Cruz, C.D.; Chen, C.T.; Xu, Y.; Shen, X.; et al. LaMn3 Ni2 Mn2 O12 : An
A-and B-site ordered quadruple perovskite with A-site tuning orthogonal spin ordering. Chem. Mater. 2016, 28, 8988–8996.
[CrossRef]
29. Liu, M.; Hu, C.-E.; Cheng, C.; Chen, X.R. A–B-intersite-dependent magnetic order and electronic structure of LaMn3 Ni2 Mn2 O12 :
A first-principles study. J. Phys. Chem. C 2018, 122, 1946–1954. [CrossRef]
30. Shannon, R.D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta
Crystallogr. 1976, A32, 751–767. [CrossRef]
31. Belik, A.A.; Yi, W. High-pressure synthesis, crystal chemistry and physics of perovskites with small cations at the A site. J. Phys.
Condens. Matter 2014, 26, 163201. [CrossRef]
32. Byeon, S.H.; Lufaso, M.W.; Parise, J.B.; Woodward, P.M.; Hansen, T. High-pressure synthesis and characterization of perovskites
with simultaneous ordering of both the A- and B-site cations, CaCu3 Ga2 M2 O12 (M = Sb, Ta). Chem. Mater. 2003, 15, 3798–3804.
[CrossRef]
33. Byeon, S.H.; Lee, S.S.; Parise, J.B.; Woodward, P.M.; Hur, N.H. High-pressure synthesis of metallic perovskite ruthenate
CaCu3 Ga2 Ru2 O12 . Chem. Mater. 2004, 16, 3697–3701. [CrossRef]
34. Byeon, S.H.; Lee, S.S.; Parise, J.B.; Woodward, P.M.; Hur, N.H. New ferrimagnetic oxide CaCu3 Cr2 Sb2 O12 : High-pressure
synthesis, structure, and magnetic properties. Chem. Mater. 2005, 17, 3552–3557. [CrossRef]
Molecules 2024, 29, 5488 17 of 17

35. Deng, H.S.; Liu, M.; Dai, J.H.; Hu, Z.W.; Kuo, C.Y.; Yin, Y.Y.; Yang, J.Y.; Wang, X.; Zhao, Q.; Xu, Y.; et al. Strong enhancement of
spin ordering by A-site magnetic ions in the ferrimagnet CaCu3 Fe2 Os2 O12 . Phys. Rev. B 2016, 94, 024414. [CrossRef]
36. Wang, X.; Liu, Z.; Deng, H.; Agrestini, S.; Chen, K.; Lee, J.-F.; Lin, H.-J.; Chen, C.-T.; Choueikani, F.; Ohresser, P.; et al.
Comparative study on the magnetic and transport properties of B-site ordered and disordered CaCu3 Fe2 Os2 O12 . Inorg. Chem. 2022,
61, 16929–16935. [CrossRef]
37. Wang, X.; Liu, M.; Shen, X.D.; Liu, Z.H.; Hu, Z.W.; Chen, K.; Ohresser, P.; Nataf, L.; Baudelet, F.; Lin, H.-J.; et al. High-temperature
ferrimagnetic half metallicity with wide spin-up energy gap in NaCu3 Fe2 Os2 O12 . Inorg. Chem. 2019, 58, 320–326. [CrossRef]
38. Ye, X.; Liu, Z.; Wang, W.; Hu, Z.; Lin, H.-J.; Weng, S.-C.; Chen, C.-T.; Yu, R.; Tjeng, L.-H.; Long, Y.W. High-pressure synthesis and
spin glass behavior of a Mn/Ir disordered quadruple perovskite CaCu3 Mn2 Ir2 O12 . J. Phys. Condens. Matter 2020, 32, 075701.
[CrossRef]
39. Li, H.P.; Zhang, Q.; Zhu, Z.P.; Ge, Z.Z.; Li, C.S.; Meng, J.; Tian, Y. Unraveling the effect of B-site antisite defects on the electronic
and magnetic properties of the quadruple perovskite CaCu3 Fe2 Nb2 O12 . Phys. Chem. Chem. Phys. 2019, 21, 3059–3065. [CrossRef]
40. Guo, J.; Shen, X.D.; Liu, Z.H.; Qin, S.J.; Wang, W.P.; Ye, X.B.; Liu, G.X.; Yu, R.C.; Lin, H.-J.; Chen, C.-T.; et al. High-pressure
synthesis of a B-site Co2+ /Mn4+ disordered quadruple perovskite LaMn3 Co2 Mn2 O12 . Inorg. Chem. 2020, 59, 12445–12452.
[CrossRef]
41. Liu, Z.; Sun, Q.; Ye, X.; Wang, X.; Zhou, L.; Shen, X.; Chen, K.; Nataf, L.; Baudelet, F.; Agrestini, S.; et al. Quadruple perovskite
oxide LaCu3 Co2 Re2 O12 : A ferrimagnetic half metal with nearly 100% B-site degree of order. Appl. Phys. Lett. 2020, 117, 152402.
[CrossRef]
42. Li, S.M.; Shu, M.F.; Wang, M.; Pan, C.B.; Zhao, G.C.; Yin, L.H.; Song, W.H.; Yang, J.; Zhu, X.B.; Sun, Y.P. Critical behavior at
paramagnetic to ferrimagnetic phase transition in A-site ordered perovskite CaCu3 Cr2 Nb2 O12 . Phys. B Condens. Matter 2023,
648, 414376. [CrossRef]
43. Morimura, A.; Kamiyama, S.; Hayashi, N.; Yamamoto, H.; Yamada, I. High-pressure syntheses, crystal structures, and magnetic
properties of novel quadruple perovskite oxides LaMn3 Ru2 Mn2 O12 and LaMn3 Ru2 Fe2 O12 . J. Alloys Comp. 2023, 968, 172263.
[CrossRef]
44. Zhang, J.; Liu, Z.H.; Ye, X.B.; Wang, X.; Lu, D.B.; Zhao, H.T.; Pi, M.C.; Chen, C.-T.; Chen, J.-L.; Kuo, C.-Y.; et al. High-pressure
synthesis of quadruple perovskite oxide CaCu3 Cr2 Re2 O12 with a high ferrimagnetic Curie temperature. Inorg. Chem. 2024,
63, 3499–3505. [CrossRef] [PubMed]
45. Kumar, L.; Datta, J.; Sen, S.; Ray, P.P.; Mandal, T.K. Ambient pressure synthesis and properties of LaCu3 Fe2 TiSbO12 : New A-site
ordered ferrimagnetic quadruple perovskite. J. Solid State Chem. 2021, 302, 122433. [CrossRef]
46. Kumar, L.; Sen, S.; Mandal, T.K. Ambient pressure synthesis and structure and magnetic properties of a new A- and B-site ordered
multinary quadruple perovskite. Dalton Trans. 2024, 53, 11060–11070. [CrossRef]
47. Brese, N.E.; O’Keeffe, M. Bond-valence parameters for solids. Acta Crystallogr. 1991, B47, 192–197. [CrossRef]
48. Tanaka, M.; Katsuya, Y.; Matsushita, Y.; Sakata, O. Development of a synchrotron powder diffractometer with a one-dimensional
X-ray detector for analysis of advanced materials. J. Ceram. Soc. Jpn. 2013, 121, 287–290. [CrossRef]
49. Izumi, F.; Ikeda, T. A Rietveld-analysis program RIETAN-98 and its applications to zeolites. Mater. Sci. Forum 2000,
321–324, 198–205. [CrossRef]

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual
author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to
people or property resulting from any ideas, methods, instructions or products referred to in the content.