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[Alexei A. Belik](https://orcid.org/0000-0001-9031-2355), [Ran Liu](https://orcid.org/0000-0002-1659-2325), [Lei Zhang](https://orcid.org/0000-0003-1173-4328), [Yoshitaka Matsushita](https://orcid.org/0000-0002-4968-8905), [Kazunari Yamaura](https://orcid.org/0000-0003-0390-8244)

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[Charge- and Orbital-Order Transitions in the A-Site-Ordered Quadruple Perovskite NdCuMn6O12](https://mdr.nims.go.jp/datasets/5ba4a21e-ef59-4a1e-a9f5-e46bd8ed08a1)

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Academic Editor: Marius AndruhReceived: 21 May 2026Revised: 18 June 2026Accepted: 24 June 2026Published: 26 June 2026Copyright: © 2026 by the authors.Licensee MDPI, Basel, Switzerland.This article is an open access articledistributed under the terms andconditions of the Creative CommonsAttribution (CC BY) license.ArticleCharge- and Orbital-Order Transitions in the A-Site-OrderedQuadruple Perovskite NdCuMn6O12Alexei A. Belik 1,* , Ran Liu 1,2,3 , Lei Zhang 1,2, Yoshitaka Matsushita 4 and Kazunari Yamaura 1,21 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, Japan3 Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1,Osaka 567-0047, Ibaraki, Japan4 National Institute for Materials Science (NIMS), Sengen 1-2-1, Tsukuba 305-0047, Ibaraki, Japan;matsushita.yoshitaka@nims.go.jp* Correspondence: alexei.belik@nims.go.jpAbstractAMn7O12 perovskites (with A = divalent elements) show complex structural and mag-netic transitions including incommensurate orbital density waves and coupled/decoupledmodulated spin helicity originating from charge-ordered Mn3+/Mn4+ cations with the 3:1ratio at the B perovskite sites and unusual apically compressed Jahn–Teller distortionsof MnO6 octahedra. The same Mn3+:Mn4+ ratio can be achieved in RCuMn6O12 compo-sitions, where R is a trivalent rare-earth cation. Therefore, the comparison in behaviorof AMn7O12 and RCuMn6O12 is of interest. In this work, the A-site-ordered quadrupleperovskite NdCuMn6O12 was prepared by a high-pressure high-temperature method. Itsstructural properties were investigated by synchrotron powder X-ray diffraction between100 K and 350 K and laboratory powder X-ray diffraction between 5 K and 300 K. It showsa first-order structural phase transition from Im-3 symmetry (at high temperatures) to R-3symmetry near 292 K. The structural transition is accompanied by charge (Mn3+/Mn4+) andunusual orbital (on the Jahn–Teller active Mn3+ cations located in MnO6 octahedra) orders.However, no additional structural/orbital modulations were found at lower temperaturesin comparison with AMn7O12. Magnetic properties were investigated by temperature- andfield-dependent magnetization and specific heat measurements, where a ferrimagnetictransition was found near 120 K. In addition, low-temperature magnetic anomalies wereobserved near 20 K, probably originating from the Nd sublattice.Keywords: A-site-ordered quadruple perovskites; orbital order; charge order; high-pressure synthesis1. IntroductionManganites have played an important role in the science of perovskite-structurematerials since the 1950s [1,2]. They were used for understanding the interplay betweencharge, spin, and orbital degrees of freedom and the crystal lattice in transition-metaloxides and developing such concepts as small polarons, double exchange, electron–phononcouplings, and Jahn–Teller (JT) distortions [3–5].Inorganics 2026, 14, 174 https://doi.org/10.3390/inorganics14070174https://crossmark.crossref.org/dialog?doi=10.3390/inorganics14070174&domain=pdf&date_stamp=2026-06-26https://creativecommons.org/licenses/by/4.0/https://creativecommons.org/licenses/by/4.0/https://www.mdpi.com/journal/inorganicshttps://www.mdpi.comhttps://orcid.org/0000-0001-9031-2355https://orcid.org/0000-0002-1659-2325https://orcid.org/0000-0002-4968-8905https://orcid.org/0000-0003-0390-8244https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 2 of 17A lot of papers were published on simple perovskite R1−xAxMnO3 manganites,where R is a rare-earth cation and A is a divalent cation [3–5], and detailed composition–temperature phase diagrams were constructed [3–6]. Charge-ordering (CO) phenomenawere often observed at some special doping levels, such as near x = 0.5 (half-doped), x = 1/3(one-third-doped), x = 1/4 (quarter-doped), and others. In addition to different CO patterns,orbital ordering (OO) on sites containing Mn3+ cations is realized, and complex spin order-ings take place coupled with underlying charge-ordered and orbital-ordered structures.A-site-ordered quadruple perovskites [7–11] with the general composition of AA′3B4O12form a different playground to manipulate charge, spin, and orbital degrees of freedom.Such manganites, AMn3Mn4O12 or AMn7O12 in short [10,11], intrinsically have differ-ent ratios of Mn3+ and Mn4+ cations (at the perovskite B sites) without any doping, de-pending on the oxidation state of the A cation. With A = Na+ [12,13], the Mn4+:Mn3+ratio is 1:1 (half-doped). With A = Mn2+, Ca2+, Cd2+, Sr2+, Hg2+, and Pb2+ [14–23], theMn4+:Mn3+ ratio is 1:3 (quarter-doped). Among different AMn7O12 compounds, CaMn7O12(= [Ca2+Mn33+][Mn33+Mn4+]O12) was the most studied compound because it is the onlycomposition that can be prepared at ambient pressure [15]. CaMn7O12 [10] shows a COtransition below TCO = 409–448 K (TCO is a CO transition temperature) with the Im-3symmetry above TCO and R-3 symmetry below TCO. The R-3 structure has apically com-pressed Mn3+O6 octahedra with four longer and two shorter Mn–O distances [16] whileusual JT systems have two longer and four shorter Mn–O distances. CaMn7O12 showsanother transition below TOO = 260 K with an incommensurate structural modulation andpropagation vector, kS = (0, 0, ~0.92). The incommensurate structure has a complex mod-ulation of Mn–O bond distances interpreted as an incommensurate orbital density wavelocalized on the B-site Mn3+ cations, and the majority of MnO6 octahedra in this structureare locally elongated along one of two axes with certain periods resulting in the apparentapical compression of MnO6 octahedra on average. CaMn7O12 shows the first long-rangemagnetic ordering transition below TN1 = 90 K with an incommensurate propagationvector locked to the structural modulation [18]. Below the second magnetic transition atTN2 = 48 K, the magnetic structure delocks from the structural modulation giving rise to acomplex multi-k magnetic ground state [18]. Magnetic structures of CaMn7O12 break theinversion symmetry producing spin-induced ferroelectric polarization [17,18]. The similarpicture of complex structural and magnetic phase transitions is realized in other membersof the AMn7O12 series with A = Mn, Cd, Sr, Hg, and Pb [10,20–23]. Therefore, AMn7O12compounds and their variations, such as CaCuxMn7−xO12 solid solutions [24–37] with0 ≤ x ≤ 3, have attracted a lot of attention in the literature. For example, compounds withlarge Cu contents show robust ferrimagnetic properties above room temperature [31,37],large low-field magnetoresistance [32,33,36], and magnetocaloric properties [34]. AMn7O12compounds and their variations show good catalytic properties [38].The Mn4+: Mn3+ ratio of 1:3 at the B sites can also be achieved in the followingcompositions: RCuMn6O12 (=[R3+Cu2+Mn23+][Mn33+Mn4+]O12), where R is a trivalent rare-earth cation, which are the members of more general solid solutions with the compositionof RCuxMn7−xO12 [39–54] and with x = 1. Therefore, it could be interesting to compare thestructural and magnetic properties of the AMn7O12 and RCuMn6O12 series. In this work,we prepared one member of the RCuMn6O12 series with R = Nd using a high-pressurehigh-temperature method. NdCuMn6O12 shows a CO transition near 290 K from Im-3symmetry (above 290 K) to R-3 symmetry (below 290 K). The R-3 symmetry remains downat 5 K without any additional structural distortions/modulations in comparison with theAMn7O12 series. NdCuMn6O12 also shows a ferrimagnetic transition below 120 K and asecond magnetic transition near 20 K probably originating from the Nd sublattice, again incomparison with the AMn7O12 series.https://doi.org/10.3390/inorganics14070174https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 3 of 172. Results and DiscussionNo impurity reflections were detected even on high-resolution, high-intensity syn-chrotron powder X-ray diffraction (XRD) data of the prepared NdCuMn6O12 samplesconfirming the high quality of the samples. However, room-temperature (RT) XRD data(laboratory and synchrotron) showed the presence of two phases, cubic Im-3 and trigonalR-3, because a structural phase transition temperature is very close to RT (292 K, see below).Therefore, we show synchrotron XRD patterns at 100 K and 350 K (not at RT) in Figure 1 todemonstrate the sample quality.   -0.20.00.20.40.60.81.01.21.45 10 15 20 25 30 35-0.10.10.30.50.75 10 15 20 25 30 35Intensity (×106   counts) 2θ  (deg): λ = 0.65298 Å Intensity (×106   counts) (a) NdCuMn6O12 T = 100 K (b) T = 350 K 0.000.020.0453.4 53.5 53.6Figure 1. Fragments (between 5◦ and 35◦) of experimental (black crosses), calculated (red line), anddifference (blue line at the bottom) synchrotron powder X-ray diffraction patterns of NdCuMn6O12at (a) T = 100 K in the R-3 phase and (b) T = 350 K in the Im-3 phase. The tick marks show possibleBragg reflection positions. The inset in (b) emphasizes the shape of reflections in the high 2θ region.The crystal structures of NdCuMn6O12 were refined by the Rietveld method fromsynchrotron XRD data. The initial structural models were taken from CaMn7O12 [16].Structural parameters of NdCuMn6O12 at some selected temperatures are summarizedin Tables 1 and 2. Experimental, calculated, and difference synchrotron XRD patterns ofNdCuMn6O12 at 100 K and 350 K are shown in Figure 1. In the cubic Im-3 modification,https://doi.org/10.3390/inorganics14070174https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 4 of 17reflections were very sharp and symmetrical (the inset of Figure 1b) indicating goodcrystallinity and homogeneity of the sample.Table 1. Structure parameters of charge-ordered NdCuMn6O12 at selected temperatures from syn-chrotron X-ray powder diffraction data.T (K) 100 150 200 250 270a (Å) 10.48252 (1) 10.48518 (1) 10.48747 (1) 10.48916 (1) 10.48927 (1)c (Å) 6.35552 (1) 6.35415 (1) 6.35544 (1) 6.35884 (1) 6.36119 (1)V (Å3) 604.8011 (7) 604.9781 (6) 605.3652 (7) 605.8845 (7) 606.1211 (8)B(Nd) (Å2) 0.145 (7) 0.183 (6) 0.237 (7) 0.282 (7) 0.299 (7)B(Mn1/Cu1)(Å2) 0.390 (8) 0.421 (8) 0.478 (8) 0.555 (9) 0.585 (9)B(Mn2) (Å2) 0.147 (9) 0.164 (8) 0.192 (8) 0.232 (9) 0.242 (9)B(Mn3) (Å2) 0.136 (16) 0.149 (15) 0.169 (15) 0.204 (16) 0.218 (17)x(O1) 0.2180 (2) 0.2181 (2) 0.2181 (2) 0.2181 (3) 0.2179 (3)y(O1) 0.2671 (3) 0.2672 (2) 0.2672 (2) 0.2672 (3) 0.2671 (3)z(O1) 0.0824 (3) 0.0821 (3) 0.0819 (3) 0.0823 (3) 0.0832 (3)B(O1) (Å2) 0.22 (4) 0.23 (4) 0.26 (4) 0.37 (4) 0.43 (4)x(O2) 0.3425 (2) 0.3423 (2) 0.3423 (2) 0.3423 (2) 0.3423 (2)y(O2) 0.5231 (2) 0.5231 (2) 0.5231 (2) 0.5230 (2) 0.5229 (2)z(O2) 0.3442 (4) 0.3441 (4) 0.3439 (3) 0.3440 (4) 0.3438 (4)B(O2) (Å2) 0.27 (4) 0.26 (4) 0.27 (4) 0.35 (4) 0.39 (4)Rwp (%) 5.54 5.31 5.25 5.46 5.78Rp (%) 3.58 3.50 3.47 3.57 3.77RB (%) 3.09 3.06 3.07 3.16 3.25Source: Synchrotron powder X-ray diffraction (λ = 0.65298 Å); used d-space range: 0.6595–7.485 Å (measuredd-space range: 0.6595–12.273 Å). Crystal system: trigonal. Space group R-3 (No. 148, hexagonal axes), Z = 3. Ndcations occupy the 3a site (0, 0, 0); Mn1/Cu1—9e site (0.5, 0, 0); Mn2—9d site (0.5, 0, 0.5); Mn3—3b site (0, 0, 0.5);O3 and O4—18f site (x, y, z). The occupation factors of the Nd, Mn2, Mn3, O1, and O2 sites are 1; the occupationof the Mn1/Cu1 site is 2/3Mn + 1/3Cu.Table 2. Structure parameters of charge-disordered NdCuMn6O12 at selected temperatures fromsynchrotron X-ray powder diffraction data.T (K) 310 350a (Å) 7.39512 (1) 7.39722 (1)V (Å3) 404.4227 (2) 404.7675 (2)B(Nd) (Å2) 0.402 (6) 0.429 (5)B(Mn1/Cu1) (Å2) 0.801 (9) 0.832 (8)B(Mn2) (Å2) 0.332 (7) 0.348 (6)y(O) 0.30559 (18) 0.30573 (16)z(O) 0.17458 (20) 0.17457 (17)B(O) (Å2) 0.51 (3) 0.58 (3)Rwp (%) 6.37 5.46Rp (%) 4.03 3.71RB (%) 4.77 4.13Source: Synchrotron powder X-ray diffraction (λ = 0.65298 Å); used d-space range: 0.6595–7.485 Å (measuredd-space range: 0.6595–12.273 Å). Crystal system: cubic. Space group Im-3 (No. 204), Z = 2. Nd cations occupy the2a site (0, 0, 0); Mn1/Cu1—6b site (0, 0.5, 0.5); Mn2—8c site (0.25, 0.25, 0.25); O—24g site (0, y, z). The occupationfactors of the Nd, Mn2, and O sites are 1; the occupation of the Mn1/Cu1 site is 2/3Mn + 1/3Cu.In the crystal structure analysis, Cu2+ cations were placed at the square-planar A′ site(together with Mn3+ cations) with a fixed occupation as 2/3Mn + 1/3Cu for the Mn1/Cu1site. Previous structural studies of similar compounds with neutron powder diffraction(which can easily distinguish between Cu and Mn) showed that Cu2+ cations are alwayslocated at the A′ site due to the strong JT effect of Cu2+ cations [25,37,41,47,53,54]. Forhttps://doi.org/10.3390/inorganics14070174https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 5 of 17unknown reasons, the available synchrotron XRD data were not so sensitive to the locationof Cu2+ cations in NdCuMn6O12 even though the Cu2+ and Mn3+ cations differ by fiveelectrons (or about 20%). For example, the refined occupation factor of the Mn1 site (whenonly Mn was placed at this site) was g(Mn1) = 1.036(1) with refined B = 0.67(9) Å2 (using the350 K data in the cubic modification because of the lower number of refined parameters).The obtained g value was within the sensitivity of the method (that is, not noticeablyhigher) as a similar value was obtained for the Nd site when refined (g(Nd) = 1.035(1)with refined B = 0.497(6) Å2). g(Mn2) was refined to be 0.983(1) with refined B = 0.289(8)Å2. Note that two other sets of synchrotron XRD data measured on different batches ofNdCuMn6O12 (at T = 380 K with λ = 0.65298 Å) gave g(Nd) = 1.015(1), g(Mn1) = 1.045(2),and g(Mn2) = 1.000(2), and g(Nd) = 1.024(1), g(Mn1) = 1.044(1), and g(Mn2) = 1.014(1). Inall cases, the occupation factor of the Mn1 site was slightly larger than that of the Mn2 site(when only Mn was placed at these sites).Figure 2 shows the temperature dependence of the lattice parameters obtained fromlaboratory and synchrotron XRD data (see also Tables S1 and S2). Note that the latticeparameters of the R-3 modification were transformed from the hexanogal axes (aH ≈ 10.5 Åand cH ≈ 6.36 Å) to the rhombohedral axes (aR ≈ 6.42 Å and αR ≈ 109.6◦; aR = (aH × β)/3,αR = 2 × arcsin(1.5/β), β = (3 + (cH/aH)2)1/2) and then to a different cell choice in therhombohedral axes (aR ≈ 7.40 Å and αR ≈ 90.3◦) for the better comparison with the cubicIm-3 modification (aC ≈ 7.40 Å (and αC = 90◦)). The two phases co-existed in a certaintemperature range near RT indicating a phase transition of the first order. There weresome differences in the aR parameter for the laboratory and synchrotron XRD data. Thesedifferences can be explained by different zero-shift parameters for different XRD sources(zero-shift parameters are usually very small for synchrotron XRD data) and by the factthat samples from different batches were used for the laboratory and synchrotron XRDmeasurements. The aR parameter gradually decreases with decreasing temperature andthen becomes nearly temperature-independent below about 100 K. The rhombohedralangle αR shows a dome-like behavior between TCO (≈292 K) and 60 K, and its temperaturebehavior changes below 50 K, where it slightly decreases with decreasing temperature.No anomalies in the lattice parameters were observed at the first magnetic transitiontemperature (TC = 120 K, see below). The R-3 modification was found to be stable belowTCO down to 5 K since no (new) modulation reflections were observed on laboratory XRDdata down to 5 K and on high-resolution, high-intensity synchrotron XRD data downto 100 K within the sensitivity of both methods. Therefore, the structural behavior ofNdCuMn6O12 is different from that of CaMn7O12 [10,16–19] below TCO.Figure 3 shows the temperature dependence of the bond lengths in NdCuMn6O12 inthe R-3 and Im-3 modifications. The Im-3 modification has one crystallographic site foroctahedral Mn cations. Therefore, this site should have an average oxidation state of +3.25.The bond-valence sum [55] value of +3.35 (at 350 K) supports the average value (for calcu-lations we used R0 = 1.76 for all Mn). The R-3 modification has two crystallographic sitesfor octahedral Mn cations. One octahedral site (Mn3) has short Mn-O distances (which areall the same and, therefore, the octahedral distortion parameter is zero). Therefore, this siteshould be occupied by Mn4+. The bond-valence sum [55] value of +3.87 (at 270 K) supportsthis assignment. For the second octahedral site (Mn2), the MnO6 octahedra have an apicallycompressed geometry with four longer Mn-O distances and two shorter Mn-O distances(and the resulting octahedral distortion parameter was about 8.4 × 10−4). Such distortionsare caused by the JT effect. This site should be occupied by Mn3+, and the bond-valencesum [55] value of +3.20 (at 270 K) supports this assignment. The same structural featurestake place in CaMn7O12 [16] below TCO. The bond-valence sum [55] values of the Nd sitesremain nearly the same (+3.20 to +3.23) in the R-3 and Im-3 modifications. The larger valueshttps://doi.org/10.3390/inorganics14070174https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 6 of 17than expected indicate that Nd3+ cations are overbonded, and this fact could be a reasonwhy NdMn7O12 [51] and NdCuMn6O12 need a high-pressure high-temperature methodfor their preparation. The bond lengths remain nearly the same at all temperatures (exceptin the vicinity of TCO). Therefore, the bond-valence sum values remain nearly constantat different temperatures. We note that the degree of charge separation [56] estimatedby bond-valence sum calculations (about 66% in our case at 270 K) is always below idealvalues as emphasized in the literature [23,56], and bond-valence calculations just indicatetendencies. The main reason seems to be the nature of bond-valence calculations as they arebased on some average parameters obtained from the statistical analysis of many reportedcrystal structures. In principle, bond-valence parameters can be adjusted for specific mate-rials and coordination numbers and environments. For example, in R3+MnO3 perovskites,where Mn definitely has the fixed oxidation state of +3 and strong JT distortions, thestandard bond-valence calculations (with R0(Mn3+) = 1.76 [55]) give values from +3.12 to+3.21 even when structural parameters determined from neutron diffraction (with preciselocalization of oxygen atoms) are used [57]. The use of R0(Mn3+) = 1.74 gives bond-valencesums close to +3.0 in RMnO3 perovskites and in the Mn2 site of NdCuMn6O12 (for theR-3 modification).7.3877.3897.3917.3937.3957.3977.3997.4010 50 100 150 200 250 300 35090.3390.3490.3590.3690.3790.3890.3990.40NdCuMn6O12 Temperature (K) Lattice parameter, aR and aC (Å) Angle, αR  (°) Im-3 R-3 SXRD SXRD SXRD Lab XRD Lab XRD TC  aR aC aR αR Figure 2. Temperature dependence of the lattice parameters of NdCuMn6O12 on heating. Theleft-hand axis shows the rhombohedral (aR) and cubic (aC) lattice parameter. The right-hand axisshows the rhombohedral angle (αR). Black and blue symbols show results from synchrotron powderX-ray diffraction (SXRD) measurements; gray symbols show results from laboratory powder X-raydiffraction (Lab XRD) measurements. The vertical arrow shows the position of the magnetic transitiontemperature, TC.The Mn-O bond lengths in NdCuMn6O12 in the R-3 modification are nearlytemperature-independent (Figure 3). Therefore, the unusual JT distortions in NdCuMn6O12do not experience any relaxation in comparison with CaMn7O12 [10,16]. However, therhombohedral distortions/angles (Figure 2) first increased with decreasing temperaturefrom 292 K to about 180 K in NdCuMn6O12; then they reduced on further cooling from180 K down to 60 K producing the dome-like behavior of the temperature dependence ofthe rhombohedral angle. Below 60 K, the rhombohedral distortion/angle is nearly locked.This behavior could be related to unusual JT distortions and their tendency to be relaxed.https://doi.org/10.3390/inorganics14070174https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 7 of 17 2.572.582.592.602.612.622.632.64100 150 200 250 300 350Nd-O2Nd-O1Nd-O (C)1.911.921.93100 150 200 250 300 350Mn1/Cu1-O1Mn1/Cu1-O2Mn1/Cu1-O (C)1.881.921.962.002.04100 150 200 250 300 350Mn2-O1Mn2-O2Mn2-O1Mn3-O2Mn2-O (C)604.7605.2605.7606.2606.7607.2100 150 200 250 300 350Temperature (K) Bond Lengths (Å) Bond Lengths (Å) Volume (Å3 ) (a) (b) (c) (d) NdCuMn6O12 12 % 74 % 93 % 100 % Mn4+ Mn3+ JT Mn3.25+ Im-3 R-3 B sites A′ sites A sites ×12 ×4 ×6 ×6 ×6 ×6 ×2 ×2 ×2 ×2 VR 1.5VC ×2 Figure 3. Temperature dependence of (a–c) bond lengths and (d) the (normalized to the R-3 cell)unit cell volume of NdCuMn6O12 on heating determined from synchrotron powder X-ray diffractionmeasurements. Data for the Im-3 phase are shown in blue. Numbers in (d) show the weight fractionof the cubic (C) Im-3 phase. The Nd-O bond lengths are given in (a), the Mn1/Cu1-O bond lengthsfor the square-planar site are given in (b), and the Mn-O bond lengths for the octahedral sites aregiven in (c).Structural behavior of NdCuMn6O12 was also investigated with differential scanningcalorimetry (DSC) (Figure 4). NdCuMn6O12 showed sharp and strong DSC anomalies onboth heating and cooling curves confirming the presence of a structural phase transitionwith TCO = 292 K (defined from peak positions on heating curves). DSC anomalies showedgood reproducibility on cycling. The sample batch used in this study showed relativelystrong and sharp DSC anomalies, and two peaks with nearly the same intensity were clearlyresolved plus a shoulder was observed from a high-temperature side. This feature couldindicate a phase separation, which was observed in NdCuxMn7−xO12 solid solutions withx = 0.1, 0.2, and 0.3 [52]. However, high-resolution synchrotron XRD data (the inset ofFigure 1b) did not detect any evidence of a phase separation. Other batches of NdCuMn6O12samples showed broader and weaker DSC anomalies (Figures S1 and S2), and no evidenceof a phase separation could be seen from such DSC data. Therefore, if a phase separation ispresent, it is quite small.https://doi.org/10.3390/inorganics14070174https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 8 of 17  -0.13-0.12-0.11-0.10-0.09200 250 300 3501st run2nd run3rd runHeat flow (W/g), heating Heat flow (W/g), cooling NdCuMn6O12 Temperature (K) (a) heating TCO = 292 K (b) cooling 0.090.100.110.120.13200 250 300 3501st run2nd runFigure 4. Differential scanning calorimetry (DSC) curves of NdCuMn6O12 (29.40 mg) during (a) heat-ing and (b) cooling. Three DSC runs were performed (and shown) to check the reproducibility.Figure 5 shows the direct current (dc) χ versus T curves of NdCuMn6O12 undermagnetic fields H = 100 Oe and 10 kOe. There were two clear anomalies (at H = 100 Oe).The first strong anomaly was observed on both zero-field-cooled (ZFC) and field-cooled oncooling (FCC) curves near TC = 120 K due to a ferrimagnetic transition. TC was definedfrom the peak positions on differential curves (Figure S3). The second anomaly (nearTN2 = 20 K) was quite broadened and was observed as a kink on the ZFC curve and agradual decrease on the FCC curve. No clear anomalies could be seen at a large magneticfield of H = 10 kOe. Neutron diffraction studies of the undoped NdMn7O12 showedthat a gradual small decrease on χ versus T curves is correlated with a gradual increasein the ordered moments on the Nd3+ sublattice [50,51], and the Nd3+ sublattice ordersantiferromagnetically with the ferrimagnetic structure formed by the Mn3+ sublattices [50].However, we note that the decrease on χ versus T curves was observed in NdMn7O12below T3 ~ 8 K at higher magnetic fields (e.g., H = 10 kOe); at smaller magnetic fields (e.g.,H = 100 Oe), the decrease already started below about 16 K. Therefore, we can assume thatthe second magnetic anomaly in NdCuMn6O12 also corresponds to the antiferromagnetic(AFM) ordering of the Nd3+ sublattice. A similar decrease in magnetic susceptibilities atlow temperatures was observed in NdCuxMn7−xO12 solid solutions with x = 1.5−3 [40,41]https://doi.org/10.3390/inorganics14070174https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 9 of 17and in NdCu3Mn3FeO12 [58]. Neutron diffraction studies of NdCu3Mn3FeO12 [58] alsoallowed suggesting AFM ordering of the Nd sublattice. However, a final conclusionabout the origin of the low-temperature susceptibility drops at small magnetic fields andthe second magnetic transition in NdCuMn6O12 can only be made from future neutrondiffraction studies. 010203040500 50 100 150 200 250 300 350ZFC, 100 OeFCC, 100 OeZFC, 10 kOeFCC, 10 kOe048120 100 200 300 400FCC, 10 kOeχ (emu×mol−1 ×Oe−1 ) Temperature (K) μeff = 10.79(2)μB θ = +184.7(6) K χ−1  (emu−1 ×mol×Oe) ×6 T C = 120 K NdCuMn6O12 μeff = 11.44(3)μB θ = +153.8(5) K μcalc = 12.258μB T CO =292 K TN2 = 20 K Figure 5. Magnetic properties of NdCuMn6O12. Zero-field-cooled (ZFC: filled curves) and field-cooled on cooling (FCC: empty curves) curves are shown at H = 100 Oe (black curves) and H = 10 kOe(red curves; multiplied by 6). The inset gives the inverse FCC χ−1 versus T curve at H = 10 kOe withCurie–Weiss fits (black lines) and fitting parameters in two regions. Vertical arrows emphasize themagnetic transition temperature (TC) and the charge-order transition temperature (TCO).Magnetic anomalies were observed at the structural phase transition of TCO = 292 K,where they could be clearly seen as a sharp step on the inverse magnetic susceptibilities (theinset of Figure 5). The Curie–Weiss law was applied to obtain effective magnetic momentsand Curie–Weiss temperatures. We fitted the FCC inverse magnetic susceptibilities (atH = 10 kOe) in the temperature ranges of 220–270 K and 320–395 K. The fitting parametersare reported in Figure 5. The Curie–Weiss temperature was positive indicating the predomi-nant ferromagnetic (FM) interactions between magnetic ions. The Curie–Weiss temperaturewas larger in the Im-3 modification in comparison with the R-3 modification, while theeffective magnetic moment was larger for the R-3 modification and closer to the expectedvalue of 12.258 µB (for the calculation, we used 3.5 µB for Nd3+, 1.732 µB for Cu2+, 4.899 µBfor Mn3+, and 3.873 µB for Mn4+ [59]). Similar behavior of inverse magnetic susceptibilitieswas observed in PrCuMn6O12 [43], CeCuMn6O12 [44], and BiCuMn6O12 [53,54].Isothermal magnetization curves (M versus H) at different temperatures are shown inFigures 6 and S4. They were typical for ferrimagnets with well-defined hysteresis near theorigin. However, they did not fully saturate and showed gradual continuous increases inmagnetization at higher magnetic fields indicating contributions from AFM interactions.The coercive field was about 600 Oe at T = 2 K, 200 Oe at T = 5 K, and ~0 Oe at T = 20 K.The magnetization values reached ≈ 17.8 µB at T = 2 and 5 K (and at H = 70 kOe) and≈17.3 µB at T = 20 K. These values are close to the expected values with the FM interactionshttps://doi.org/10.3390/inorganics14070174https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 10 of 17between Cu2+ and all Mn3+ cations and AFM interactions with Mn4+ cations, (1 + 20 − 3)= 18 µB (1 µB is the maximum ordered moment of Cu2+, 4 µB is the maximum orderedmoment of Mn3+, and 3 µB is the maximum ordered moment of Mn4+). Contributions fromNd3+ can be neglected as the ordered moments of Nd3+ are usually below 1 µB [50,58]and should be negligible at 20 K. In addition, similar saturation values were observed inCaCuxMn7−xO12 solid solutions with 1 ≤ x ≤ 2 [34], which do not have magnetic rare-earthcations, and in NdCuxMn7−xO12 solid solutions with x = 1.5 and 2 [40]. RCuxMn7−xO12and CaCuxMn7−xO12 solid solutions have a tendency to show saturation behavior for largeCu contents and gradual continuous increases in magnetization for smaller Cu contents,such as x = 1 [34,40,44,47].-18-12-6061218-80 -60 -40 -20 0 20 40 60 802 K5 K20 K50 K100 K150 K-15-10-5051015-4 -2 0 2 4Magnetization  (μB / f.u.) Magnetization  (μB / f.u.) Magnetic Field (kOe) (a) (b) NdCuMn6O12 Figure 6. Magnetic properties of NdCuMn6O12: M versus H curves at T = 2, 5, 20, 50, 100, and 150 K.Panel (a) shows the full M versus H curves, panel (b) shows the zoomed-in M versus H curves nearthe origin.Specific heat measurements (Figures 7 and S5) showed a very weak anomaly atTC = 120 K (the inset of Figure 7), while a stronger anomaly was found near TN2 = 20 K.Specific heat data unambiguously confirmed the presence of the second magnetic transition.Magnetic fields slightly suppressed specific heat anomalies at TN2 and completely smearedanomalies at TC and moved magnetic entropy to much higher temperatures. Such effects(near TC) are typical for FM and ferrimagnetic materials.https://doi.org/10.3390/inorganics14070174https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 11 of 170.00.40.81.21.60 50 100 150 200 250 3000 Oe 70 kOe0.00.40.81.20 10 20 30 400 Oe10 kOe30 kOe50 kOe70 kOeC p / T (J×K−2 ×mol−1 ) Temperature (K) 1.51.61.750 100 150 200TC = 120 K NdCuMn6O12 Figure 7. Specific heat data of NdCuMn6O12 plotted as Cp/T versus T at H = 0 Oe (black) and 70 kOe(red). The main inset shows the Cp/T versus T curves at H = 0, 10, 30, 50, and 70 kOe below 40 K.The second inset emphasizes specific heat anomalies near TC at H = 0 Oe.Ac susceptibility measurements were performed to get more information about themagnetic properties of NdCuMn6O12 (Figures 8, 9 and S6). Ac susceptibility curves weremeasured at different frequencies (Figure 8) and different ac fields (Figure 9). Somefrequency dependence was observed on the χ′ versus T curves between about 60 and110 K, while much stronger frequency dependence was observed on the χ′ ′ versus T curvesbetween about 20 and 120 K. However, such frequency dependence was not caused by anyspin-glass contributions; it was caused by interactions of the ac field with ferrimagneticdomain structures. Non-linear behavior (and the presence of interactions with domainstructures) could be more clearly seen from the dependence on the ac field (Figure 9). Theχ′ versus T curves showed sharp decreases below about 16 K with the appearance of peakson the χ′ ′ versus T curves near 8–9 K. Anomalies below 20 K showed no dependenceon the ac field, indicating the linear response. We note that very similar anomalies wereobserved below about 20 K in other members of the RCuMn6O12 series (for example, withR = Ce, Sm, and Dy [44]) especially on the χ′ ′ versus T curves. Therefore, their origin couldbe unrelated to rare-earth elements (Nd in this case) and to the presence of the secondmagnetic transition in NdCuMn6O12 at TN2.The synthesis of NdCuMn6O12 was attempted in Ref. [41]. However, because ofthe presence of large amounts of Mn-containing impurities (NdMn2O5 and Mn2O3), thecomposition of the main perovskite phase was shifted to the Cu-rich side. As a result,the main perovskite phase remained cubic down to 5 K, and no structural phase transi-tions were observed. In addition, the magnetic transition temperature was observed ata noticeably higher temperature of 206 K in Ref. [41] (in comparison with 120 K for oursample); our estimation shows that such a transition corresponds to a NdCu1.4Mn5.6O12https://doi.org/10.3390/inorganics14070174https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 12 of 17composition. Our sample was single-phase, suggesting that the target composition wasachieved, and our sample showed a structural transition from Im-3 symmetry (at high tem-peratures) to R-3 symmetry near 292 K. Such a structural transition was observed at 267 Kin PrCuMn6O12 [43], at 297 K in CeCuMn6O12 [44], and at 296 K in BiCuMn6O12 [53,54]. -0.20.00.20.40.60 20 40 60 80 100 120 140 1602 Hz7 Hz110 Hz300 Hz500 Hz051015202530350 20 40 60 80 100 120 140 1602 Hz7 Hz110 Hz300 Hz500 HzTemperature (K) Hac = 0.5 Oe f = NdCuMn6O12 f (a) (b) χ ′ (emu×mol−1 ×Oe−1 ) χ ″ (emu×mol−1 ×Oe−1 ) Figure 8. (a) The χ′ versus T and (b) χ′ ′ versus T curves of NdCuMn6O12 at different frequencies(f = 2, 7, 110, 300, 500 Hz) measured with Hac = 0.5 Oe and Hdc = 0 Oe.AA′3Mn4O12-type perovskites with the 1:3 ratio of Mn4+/Mn3+ cations at the B sitesshow CO structural transitions from Im-3 symmetry (at high temperatures) to R-3 symmetryand compressed Mn3+O6 octahedra in the average structure of the R-3 modification, whichis sometimes called an orbital disorder phase [23]. Relaxation of compressed Mn3+O6octahedra occurs through different mechanisms on further cooling [10]. As mentionedin the introduction, AMn7O12 compounds with A = Ca, Sr, and Pb show incommensu-rately modulated structures, where Mn3+O6 octahedra become locally elongated [10,20].CdMn7O12 shows a commensurately modulated structure (space group P-3), where apart of Mn3+O6 octahedra restores their typical JT distortions [10,20]. HgMn7O12 showsa polar orthorhombic distortion (space group Pnn2), an additional charge transfer, andthe restoration of typical JT distortions of Mn3+O6 octahedra [23]. BiCuMn6O12 shows ahttps://doi.org/10.3390/inorganics14070174https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 13 of 17unique re-entrant structural transition, where the R-3 modification collapses back to thecubic Im-3 modification on cooling [53,54]. CeCuMn6O12 demonstrated a phase separationbelow about 80 K [44]. Therefore, the apparent absence of any further structural transitionsin NdCuMn6O12 may need a deeper understanding and further detailed structural charac-terizations at low temperatures, including more sensitive methods such as electron andneutron diffraction. -0.20.00.20.40.60.81.01.21.40 20 40 60 80 100 120 140 1600.05 Oe, 300 Hz0.5 Oe, 300 Hz5 Oe, 300 Hz051015202530350 20 40 60 80 100 120 140 1600.05 Oe, 300 Hz0.5 Oe, 300 Hz5 Oe, 300 HzTemperature (K) Hac = f = NdCuMn6O12 0.05 Oe 5 Oe 0.5 Oe 5 Oe 0.5 Oe 0.05 Oe (a) (b) χ ′ (emu×mol−1 ×Oe−1 ) χ″ (emu×mol−1 ×Oe−1 ) Figure 9. (a) The χ′ versus T and (b) χ′ ′ versus T curves of NdCuMn6O12 at different Hac = 0.05, 0.5,and 5 Oe and one frequency of 300 Hz (under Hdc = 0 Oe).3. Materials and MethodsNdCuMn6O12 samples were prepared from stoichiometric mixtures of Nd2O3 (RareMetallic Co., Tokyo, Japan, 99.9%), CuO (Rare Metallic Co., Tokyo, Japan, 99.9%), MnO2(Alfa Aesar, Ward Hill, MA, USA, 99.99%), and Mn2O3. Single-phase Mn2O3 was preparedfrom a commercial MnO2 chemical (Rare Metallic Co., Tokyo, Japan, 99.99%) by annealingin air at 923 K for 24 h. The synthesis was performed at 6 GPa and at 1600 K for 2 h insealed Pt capsules using a belt-type high-pressure (HP) instrument. After annealing at1600 K, the samples were cooled down to room temperature (RT) by turning off the heatingcurrent, and the pressure was slowly released.https://doi.org/10.3390/inorganics14070174https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 14 of 17Laboratory powder X-ray diffraction (XRPD) data were collected at RT on a Mini-Flex600 diffractometer (Rigaku, Tokyo, Japan) using CuKα radiation (2θ range of 10−80◦, astep width of 0.02◦, and scan speed of 2◦/min). Low-temperature laboratory XRPD datawere measured on a RIGAKU SmartLab instrument (CuKα1 radiation at 45 kV and 200 mA;2θ range of 10−110◦, a step width of 0.02◦, and scan speed of 1◦/min) from 5 K to 300 K(Bragg−Brentano geometry was used for all laboratory XRPD). Synchrotron XRPD datawere measured on the BL15XU beamline (the former NIMS beamline) of SPring-8 [60]between 3.05◦ and 59.35◦ at 0.003◦ intervals in 2θ with the wavelength of λ = 0.65298 Åfrom 100 K to 350 K. The sample was placed into an open Lindemann glass capillary tube(inner diameter: 0.1 mm), which was rotated during measurements. The Rietveld analysisof all XRPD data was performed using the RIETAN-2000 program [61].Magnetic measurements were performed on a SQUID magnetometer (Quantum De-sign MPMS-XL-7T, San Diego, CA, USA) between 2 K and 350–400 K in applied fieldsof 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 temperaturesbetween −70 and 70 kOe. Frequency-dependent alternating current (ac) susceptibilitymeasurements were performed on cooling with a MPMS-1T instrument (Quantum Design,San Diego, CA, USA) at zero static dc field and at different frequencies (f ) and differentapplied oscillating magnetic fields (Hac).Specific heat, Cp, was measured on cooling from 270 K to 2 K at zero magnetic field and70 kOe and from 40 K to 2 K at H = 10, 30, and 50 kOe by a pulse relaxation method using acommercial calorimeter (Quantum Design PPMS, San Diego, CA, USA). All magnetic andspecific heat measurements were performed using pieces of pellets.Differential scanning calorimetry (DSC) curves of a powder sample (29.40 mg) wererecorded on a Mettler Toledo DSC1 STARe system (Columbus, OH, USA) between 173 Kand 423 K in open Al capsules with a heating/cooling rate of 10 K/min. Three DSC runswere performed to check the reproducibility.All the above measurements (except low-temperature laboratory XRPD because suchan experiment required a relatively large amount of a sample) were performed using thesame batch of the prepared sample.4. ConclusionsIn conclusion, the A-site-ordered quadruple perovskite NdCuMn6O12, with the pres-ence of Mn4+/Mn3+ cations with the 1:3 ratio at the B perovskite sites and therefore resem-bling CaMn7O12, was prepared by a high-pressure high-temperature method. A first-orderstructural phase transition from Im-3 symmetry (at high temperatures) to R-3 symmetrywas found near TCO = 292 K accompanied by charge ordering and orbital ordering withunusual apically compressed Jahn–Teller distortions of MnO6 octahedra. In comparisonwith CaMn7O12, no additional structural transitions were found in NdCuMn6O12 withinthe sensitivity of the used methods, indicating that compressed Jahn–Teller distortionswere not relaxed. NdCuMn6O12 shows a ferrimagnetic transition below 120 K, and thesecond magnetic transition near 20 K was found in NdCuMn6O12.Supplementary Materials: The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/inorganics14070174/s1, Figure S1 and Figure S2: Differential scanningcalorimetry (DSC) curves of a different batch of NdCuMn6O12 on (a) heating and (b) cooling. ThreeDSC runs were performed (and shown) to check the reproducibility. The peaks were broader incomparison with a sample used in the main text. The inset on (b) shows the shape of cubic reflections((6 8 2) and (10 2 0)) of synchrotron XRD data (at T = 380 K with λ = 0.65298 Å) for this sample; axes:intensity (counts/106) versus 2θ (◦); Figure S3: Magnetic properties of NdCuMn6O12. (a) Zero-field-cooled (ZFC: filled curves) and field-cooled on cooling (FCC: empty curves) curves are shown athttps://doi.org/10.3390/inorganics14070174https://www.mdpi.com/article/10.3390/inorganics14070174/s1https://www.mdpi.com/article/10.3390/inorganics14070174/s1https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 15 of 17H = 5 Oe (black curves). A different (compared with the main text) FCC curve at H = 100 Oe is shownin blue. The inset shows differential curves, dχ/dT versus T. (b) The ZFC and FCC dχ/dT versusT curves at H = 10 kOe (red curves); Figure S4: Magnetic properties of NdCuMn6O12: M versusH curves at T = 150, 200, 250, and 300 K; Figure S5: Specific heat data of NdCuMn6O12 (the samebatch as used in the main text) in a high-temperature region plotted as Cp versus T (the left-handaxis) and Cp/T versus T (the right-hand axis) at H = 0 Oe on heating (red and pink) and cooling(blue) with a step of 2 K. An H Apiezon grease was used for a better thermal contact between thesample and a sample holder. An addenda contribution was measured with a step of 4 K. Specificheat measurements are in agreement with the DSC measurements (Figure 4) and show a double-peakfeature; Figure S6: (a) The χ′ versus T and (b) χ′ ′ versus T curves of a different batch of NdCuMn6O12at different frequencies (f = 2, 7, 25, 110, 500 Hz) measured with Hac = 0.5 Oe and Hdc = 0 Oe usingMPMS3; Table S1 and Table S2: Numerical data used to plot Figure 2.Author Contributions: Conceptualization, A.A.B.; methodology, A.A.B.; validation, A.A.B.; formalanalysis, A.A.B.; investigation, A.A.B., R.L., L.Z., Y.M. 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 agreedto the published version of the manuscript.Funding: This work was partially supported by a Grant-in-Aid for Scientific Research (No. JP25K01657)from the Japan Society for the Promotion of Science.Institutional Review Board Statement: Not applicable.Informed Consent Statement: Not applicable.Data Availability Statement: The original contributions presented in this study are included in thearticle/Supplementary Materials. Further inquiries can be directed to the corresponding author.Acknowledgments: The synchrotron radiation experiments were conducted at the former NIMSbeamline (BL15XU) of SPring-8 with the approval of the former NIMS Synchrotron X-ray Station(proposal numbers: 2016B4504, 2019B4500, and 2020A4501). We thank M. Tanaka and Y. Katsuya fortheir help at SPring-8. MANA was supported by the World Premier International Research CenterInitiative (WPI), MEXT, Japan.Conflicts of Interest: The authors declare no conflicts of interest.References1. Wollan, E.O.; Koehler, W.C. Neutron diffraction study of the magnetic properties of the series of perovskite-type compounds[(1 −x)La, xCa]MnO3. Phys. Rev. 1955, 100, 545–563. [CrossRef]2. Goodenough, J.B. Theory of the role of covalence in the perovskite-type manganites [La, M(II)]MnO3. Phys. Rev. 1955, 100,564–573. [CrossRef]3. Salamon, M.B.; Jaime, M. The Physics of magnanites: Structure and transport. Rev. Mod. Phys. 2001, 73, 583–628. [CrossRef]4. Edwards, D.M. Ferromagnetism and electron-phonon coupling in the manganites. Adv. Phys. 2002, 51, 1259–1318. [CrossRef]5. Coey, J.M.D.; Viret, M.; von Molnar, S. Mixed-valence manganites. Adv. Phys. 2009, 58, 571–697. [CrossRef]6. Martin, C.; Maignan, A.; Hervieu, M.; Raveau, B. Magnetic phase diagrams of L1−xAxMnO3 manganites (L = Pr,Sm; A = Ca,Sr).Phys. Rev. B 1999, 60, 12191–12199.7. Vasil’ev, A.N.; Volkova, O.S. New functional materials AC3B4O12 (Review). Low. Temp. Phys. 2007, 33, 895–914. [CrossRef]8. Long, Y. A-site ordered quadruple perovskite oxides AA’3B4O12. Chin. Phys. B 2016, 25, 078108. [CrossRef]9. Ding, J.; Zhu, X.H. Research progress on quadruple perovskite oxides. J. Mater. Chem. C 2024, 12, 9510–9561. [CrossRef]10. Belik, A.A.; Johnson, R.D.; Khalyavin, D.D. The rich physics of A-site-ordered quadruple perovskite manganites AMn7O12.Dalton Trans. 2021, 50, 15458–15472. [CrossRef] [PubMed]11. Solana-Madruga, E.; Arevalo-Lopez, A.M. High-pressure A-site manganites: Structures and magnetic properties. J. Solid StateChem. 2022, 315, 123470. [CrossRef]12. Prodi, A.; Gilioli, E.; Gauzzi, A.; Licci, F.; Marezio, M.; Bolzoni, F.; Huang, Q.; Santoro, A.; Lynn, J.W. Charge orbital and spinordering phenomena in the mixed valence manganite (NaMn3+3)(Mn3+2Mn4+2)O12. Nat. Mater. 2004, 3, 48–52. [PubMed]https://doi.org/10.3390/inorganics14070174https://doi.org/10.1103/physrev.100.545https://doi.org/10.1103/physrev.100.564https://doi.org/10.1103/revmodphys.73.583https://doi.org/10.1080/00018730210140805https://doi.org/10.1080/00018730903363184https://doi.org/10.1063/1.2747047https://doi.org/10.1088/1674-1056/25/7/078108https://doi.org/10.1039/d4tc01467ghttps://doi.org/10.1039/d1dt02992dhttps://www.ncbi.nlm.nih.gov/pubmed/34632992https://doi.org/10.1016/j.jssc.2022.123470https://www.ncbi.nlm.nih.gov/pubmed/14704785https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 16 of 1713. Prodi, A.; Daoud-Aladine, A.; Gozzo, F.; Schmitt, B.; Lebedev, O.; van Tendeloo, G.; Gilioli, E.; Bolzoni, F.; Aruga-Katori, H.;Takagi, H.; et al. Commensurate structural modulation in the charge- and orbitally ordered phase of the quadruple perovskite(NaMn3)Mn4O12. Phys. Rev. B 2014, 90, 180101. [CrossRef]14. Bochu, B.; Chenavas, J.; Joubert, J.C.; Marezio, M. High pressure synthesis and crystal structure of a new series of perovskite-likecompounds CMn7O12 (C = Na, Ca, Cd, Sr, La, Nd). J. Solid State Chem. 1974, 11, 88–93. [CrossRef]15. Horowitz, H.S.; Longo, J.M. Phase relations in the Ca-Mn-O system. Mater. Res. Bull. 1978, 13, 1359–1369. [CrossRef]16. Bochu, B.; Buevoz, J.L.; Chenavas, J.; Collomb, A.; Joubert, J.C.; Marezio, M. Bond lengths in [CaMn3](Mn4)O12: A new Jahn–Tellerdistortion of Mn3+ octahedral. Solid State Commun. 1980, 36, 133–138. [CrossRef]17. Johnson, R.D.; Chapon, L.C.; Khalyavin, D.D.; Manuel, P.; Radaelli, P.G.; Martin, C. Giant improper ferroelectricity in the ferroaxialmagnet CaMn7O12. Phys. Rev. Lett. 2012, 108, 067201. [CrossRef] [PubMed]18. Johnson, R.D.; Khalyavin, D.D.; Manuel, P.; Bombardi, A.; Martin, C.; Chapon, L.C.; Radaelli, P.G. Modulated spin helicitystabilized by incommensurate orbital density waves in a quadruple perovskite manganite. Phys. Rev. B 2016, 93, 180403.[CrossRef]19. Perks, N.J.; Johnson, R.D.; Martin, C.; Chapon, L.C.; Radaelli, P.G. Magneto-orbital helices as a route to coupling magnetism andferroelectricity in multiferroic CaMn7O12. Nat. Commun. 2012, 3, 1277. [CrossRef] [PubMed]20. Johnson, R.D.; Khalyavin, D.D.; Manuel, P.; Radaelli, P.G.; Glazkova, I.S.; Terada, N.; Belik, A.A. Magneto-orbital ordering in thedivalent A-site quadruple perovskite manganites AMn7O12 (A = Sr, Cd, and Pb). Phys. Rev. B 2017, 96, 054448. [CrossRef]21. Locherer, T.; Dinnebier, R.; Kremer, R.K.; Greenblatt, M.; Jansen, M. Synthesis and properties of a new quadruple perovskite:A-site-ordered PbMn3Mn4O12. J. Solid State Chem. 2012, 190, 277–284. [CrossRef]22. Ovsyannikov, S.V.; Abakumov, A.M.; Tsirlin, A.A.; Schnelle, W.; Egoavil, R.; Verbeeck, J.; Van Tendeloo, G.; Glazyrin, K.V.;Hanfland, M.; Dubrovinsky, L. Perovskite-like Mn2O3: A path to new manganites. Angew. Chem. Int. Ed. 2013, 52, 1494–1498.[CrossRef]23. Chen, W.T.; Wang, C.W.; Wu, H.C.; Chou, F.C.; Yang, H.D.; Simonov, A.; Senn, M.S. Improper ferroelectric polarization in aperovskite driven by intersite charge transfer and ordering. Phys. Rev. B 2018, 97, 144102. [CrossRef]24. Troyanchuk, I.O.; Balyko, L.V.; Bashkirov, L.A. Crystal structure phase transitions in the perovskites A(Cu1−xMnx)Mn4O12(A = Na+, Ca2+, Y3+, La3+). Cryst. Res. Technol. 1986, 21, 705–710. [CrossRef]25. Slawinski, W.; Przenioslo, R.; Sosnowska, I.; Bieringer, M.; Margiolaki, I.; Fitch, A.N.; Suard, E. Phase coexistence inCaCuxMn7−xO12 solid solutions. J. Solid State Chem. 2006, 179, 2443–2451.26. Slawinski, W.; Przenioslo, R.; Sosnowska, I.; Bieringer, M.; Margiolaki, I.; Fitch, A.N.; Suard, E. Charge ordering inCaCuxMn7−xO12 (x = 0.0 and 0.1) compounds. J. Phys. Condens. Matter 2008, 20, 104239.27. Slawinski, W.; Przenioslo, R.; Sosnowska, I.; Bieringer, M. Structural and magnetic modulations in CaCuxMn7−xO12. J. Phys.Condens. Matter 2010, 22, 186001. [PubMed]28. Sławiński, W.; Przeniosło, R.; Sosnowska, I.; Bieringer, M.; Margiolakic, I.; Suard, E. Modulation of atomic positions inCaCuxMn7−xO12 (x ≤ 0.1). Acta Crystallogr. Sec. B 2009, 65, 535–542. [CrossRef] [PubMed]29. Slawinski, W.; Przenioslo, R.; Sosnowska, I.; Petrícek, V. Helical screw type magnetic structure of the multiferroic CaMn7O12 withlow Cu-doping. Acta Crystallogr. Sec. B 2012, 68, 240–249.30. Glazkova, I.S.; Rusakov, V.S.; Sobolev, A.V.; Matsnev, M.E.; Gapochka, A.M.; Gubaidulina, T.V.; Presniakov, I.A. Probe Mössbauerdiagnostics of charge ordering in manganites CaCuxMn7−xO12 (0 ≤ x ≤ 1). J. Exp. Theor. Phys. 2019, 129, 1017–1028. [CrossRef]31. Chenavas, J.; Joubert, M.; Marezio, J.C.; Bochu, B. The synthesis and crystal structure of CaCu3Mn4O12: A new ferromagnetic-perovskite-like compound. J. Solid State Chem. 1975, 14, 25–32. [CrossRef]32. Zeng, Z.; Greenblatt, M.; Subramanian, M.A.; Croft, M. Large low-field magnetoresistance in perovskite-type CaCu3Mn4O12without double exchange. Phys. Rev. Lett. 1999, 82, 3164–3167. [CrossRef]33. Sánchez-Benítez, J.; Prieto, C.; de Andrés, A.; Alonso, J.A.; Martínez-Lope, M.J.; Casais, M.T. Evidence of two different states inCaCu3Mn4O12 derivatives with colossal magnetoresistance. Phys. Rev. B 2004, 70, 024419. [CrossRef]34. Zhang, Q.; Bréard, Y.; Guillou, F.; Hardy, V. Investigation of the magnetocaloric effect in double distorted perovskitesCa(Cu3−xMnx)Mn4O12 (1 ≤ x ≤ 2): From standard ferrimagnetism to glassy ferrimagnetism. Phys. Rev. B 2011, 84, 224430.[CrossRef]35. Volkova, O.; Goodilin, E.; Vasiliev, A.; Khomskii, D.; Tristan, N.; Kerschl, P.; Skourski, Y.; Mueller, K.-H.; Buechner, B. CaCuMn6O12vs. CaCu2Mn5O12: A comparative study. J. Exp. Theor. Phys. Lett. 2005, 82, 642–645. [CrossRef]36. Zeng, Z.; Greenblatt, M.; Sunstrom, J.E.; Croft, M.; Khalid, S. Giant magnetoresistance in CaCu3Mn4O12-based oxides withperovskite-type structure. J. Solid State Chem. 1999, 147, 185–198. [CrossRef]37. Sánchez-Benítez, J.; Alonso, J.A.; Martínez-Lope, M.J.; Casais, M.T.; Martínez, J.L.; de Andrés, A.; Fernández-Díaz, M.T.Preparation, crystal and magnetic structure, and magnetotransport properties of the double perovskite CaCu2.5Mn4.5O12. Chem.Mater. 2003, 15, 2193–2200. [CrossRef]38. Yamada, I. Novel catalytic properties of quadruple perovskites. Sci. Tech. Adv. Mater. 2017, 18, 541–548. [CrossRef] [PubMed]https://doi.org/10.3390/inorganics14070174https://doi.org/10.1103/physrevb.90.180101https://doi.org/10.1016/0022-4596(74)90102-9https://doi.org/10.1016/0025-5408(78)90127-7https://doi.org/10.1016/0038-1098(80)90668-7https://doi.org/10.1103/physrevlett.108.067201https://www.ncbi.nlm.nih.gov/pubmed/22401114https://doi.org/10.1103/physrevb.93.180403https://doi.org/10.1038/ncomms2294https://www.ncbi.nlm.nih.gov/pubmed/23232407https://doi.org/10.1103/physrevb.96.054448https://doi.org/10.1016/j.jssc.2012.02.036https://doi.org/10.1002/anie.201210136https://doi.org/10.1103/physrevb.97.144102https://doi.org/10.1002/crat.2170210603https://www.ncbi.nlm.nih.gov/pubmed/21393695https://doi.org/10.1107/s0108768109025300https://www.ncbi.nlm.nih.gov/pubmed/19767675https://doi.org/10.1134/s1063776119110104https://doi.org/10.1016/0022-4596(75)90358-8https://doi.org/10.1103/physrevlett.82.3164https://doi.org/10.1103/physrevb.70.024419https://doi.org/10.1103/physrevb.84.224430https://doi.org/10.1134/1.2166912https://doi.org/10.1006/jssc.1999.8212https://doi.org/10.1021/cm0212616https://doi.org/10.1080/14686996.2017.1350557https://www.ncbi.nlm.nih.gov/pubmed/28970864https://doi.org/10.3390/inorganics14070174Inorganics 2026, 14, 174 17 of 1739. Samaras, D.; Bochu, B.; Joubert, J.C. Synthesis, composition, and magnetic properties of the ferrimagnetic NdCu3−xMn4+xO12perovskite-like phases. J. Solid State Chem. 1984, 53, 323–328. [CrossRef]40. Zhang, Q.; Bréard, Y.; Hardy, V. Spin-glass-like state and reversible room-temperature magnetocaloric effect in double distortedperovskites Nd(Cu3−xMnx)Mn4O12. Inorg. Chem. 2022, 61, 5792–5799. [CrossRef] [PubMed]41. Retuerto, M.; Martínez-Lope, M.J.; Sánchez-Benítez, J.; García-Hernández, M.; Fernández-Díaz, M.T.; Alonso, J.A. Synthesis,magnetic properties, and neutron diffraction study of the complex perovskites R(Cu3−xMnx)Mn4O12 (R = Pr, Nd and x = 1, 2).J. Appl. Phys. 2010, 108, 083905. [CrossRef]42. Sánchez-Benítez, J.; Alonso, J.A.; Falcón, H.; Martínez-Lope, M.J.; de Andrés, A.; Fernández-Díaz, M.T. Preparation under highpressures and neutron diffraction study of new ferromagnetic RCu3Mn4O12 (R = Pr, Sm, Eu, Gd, Dy, Ho, Tm, Yb) perovskites.J. Phys. Condens. Matter. 2005, 17, S3063. [CrossRef]43. Zhang, W.; Yao, L.D.; Yang, L.X.; Liu, Z.X.; Jin, C.Q.; Yu, R.C. Charge ordering in PrCuMn6O12 and its behavior under pressure.J. Appl. Phys. 2010, 107, 023914. [CrossRef]44. Zhang, L.; Matsushita, Y.; Katsuya, Y.; Tanaka, M.; Yamaura, K.; Belik, A.A. Charge and orbital orders and structural instability inhigh-pressure quadruple perovskite CeCuMn6O12. J. Phys. Condens. Matter. 2018, 30, 074003. [CrossRef] [PubMed]45. Sanchez-Benitez, J.; Alonso, J.A.; de Andres, A.; Martinez-Lope, M.J.; Martinez, J.L.; Munoz, A. Peculiar magnetic behavior of theTbCu3Mn4O12 complex perovskite. Chem. Mater. 2005, 17, 5070–5076.46. Alonso, J.A.; Sánchez-Benítez, J.; de Andrés, A.; Martínez-Lope, M.J.; Casais, M.T.; Martínez, J.L. Enhanced magnetoresistance inthe complex perovskite LaCu3Mn4O12. Appl. Phys. Lett. 2003, 83, 2623–2625. [CrossRef]47. Muñoz, A.; Martínez-Lope, M.J.; Retuerto, M.; Falcón, H.; Alonso, J.A. Ferromagnetic behavior in La(Cu3−xMnx)Mn4O12 (x = 1,2) perovskites. J. Appl. Phys. 2008, 104, 083911. [CrossRef]48. Sanchez-Benitez, J.; Alonso, J.A.; Martinez-Lope, M.J.; de Andres, A.; Fernandez-Diaz, M.T. Enhancement of the Curie temperaturealong the perovskite series RCu3Mn4O12 driven by chemical pressure of R3+ cations (R = rare rarths). Inorg. Chem. 2010, 49,5679–5685. [PubMed]49. Sánchez-Benítez, J.; Martínez-Lope, M.J.; Alonso, J.A. Preparation at moderate pressures, crystal and magnetic structure andmagnetotransport of the ferrimagnetic CeCu3Mn4O12 perovskite. J. Appl. Phys. 2010, 107, 103904. [CrossRef]50. Johnson, R.D.; Khalyavin, D.D.; Manuel, P.; Zhang, L.; Yamaura, K.; Belik, A.A. Magnetic structures of the rare-earth quadrupleperovskite manganites RMn7O12. Phys. Rev. B 2018, 98, 104423. [CrossRef]51. Belik, A.A.; Liu, R.; Zhang, L.; Terada, N.; Tanaka, M.; Yamaura, K. Multiple magnetic transitions and complex magnetic behaviourof the perovskite manganite NdMn7O12. J. Solid State Chem. 2022, 309, 122969. [CrossRef]52. Belik, A.A.; Liu, R.; Yamaura, K. Phase separation phenomena in lightly Cu-doped A-site-ordered quadruple perovskiteNdMn7O12. Molecules 2025, 30, 4561. [CrossRef] [PubMed]53. Belik, A.A.; Matsushita, Y.; Khalyavin, D.D. Reentrant structural transitions and collapse of charge and orbital orders in quadrupleperovskites. Angew. Chem. Int. Ed. 2017, 56, 10423. [CrossRef] [PubMed]54. Belik, A.A.; Matsushita, Y.; Tanaka, M.; Johnson, R.D.; Khalyavin, D.D. A plethora of structural transitions, distortions andmodulations in Cu-doped BiMn7O12 quadruple perovskites. J. Mater. Chem. C 2021, 9, 10232–10242. [CrossRef]55. Brese, N.E.; O’Keeffe, M. Bond-valence parameters for solids. Acta Crystallogr. Sec. B 1991, 47, 192–197. [CrossRef]56. Attfield, J.P. Charge ordering in transition metal oxides. Solid State Sci. 2006, 8, 861–867. [CrossRef]57. Alonso, J.A.; Martinez-Lope, M.J.; Casais, M.T.; Fernandez-Diaz, M.T. Evolution of the Jahn-Teller distortion of MnO6 octahedrain RMnO3 perovskites (R = Pr, Nd, Dy, Tb, Ho, Er, Y): A neutron diffraction study. Inorg. Chem. 2000, 39, 917–923. [CrossRef][PubMed]58. Sánchez-Benítez, J.; Kayser, P.; Martínez-Lope, M.J.; de la Calle, C.; Retuerto, M.; Fernandez-Díaz, M.T.; Alonso, J.A. High-pressurepreparation and characterization of new metastable oxides: The case of NdCu3Mn3MO12 (M= Fe, Cr). J. Phys. Conf. Ser. 2011, 325,012002. [CrossRef]59. Kittel, C.; McEuen, P. Introduction to Solid State Physics; John Wiley & Sons, Inc.: New York, NY, USA, 2005.60. Tanaka, M.; Katsuya, Y.; Matsushita, Y.; Sakata, O. Development of a synchrotron powder diffractometer with a one-dimensionalX-ray detector for analysis of advanced materials. J. Ceram. Soc. Jpn. 2013, 121, 287–290. [CrossRef]61. Izumi, F.; Ikeda, T. A Rietveld-analysis program RIETAN-98 and its applications to zeolites. Mater. Sci. Forum 2000, 321–324,198–205. 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MDPI and/or the editor(s) disclaim responsibility for any injury topeople or property resulting from any ideas, methods, instructions or products referred to in the content.https://doi.org/10.3390/inorganics14070174https://doi.org/10.1016/0022-4596(84)90109-9https://doi.org/10.1021/acs.inorgchem.1c03895https://www.ncbi.nlm.nih.gov/pubmed/35389638https://doi.org/10.1063/1.3498807https://doi.org/10.1088/0953-8984/17/40/009https://doi.org/10.1063/1.3294608https://doi.org/10.1088/1361-648x/aaa5e4https://www.ncbi.nlm.nih.gov/pubmed/29359703https://doi.org/10.1063/1.1611647https://doi.org/10.1063/1.3000617https://www.ncbi.nlm.nih.gov/pubmed/20462198https://doi.org/10.1063/1.3369444https://doi.org/10.1103/physrevb.98.104423https://doi.org/10.1016/j.jssc.2022.122969https://doi.org/10.3390/molecules30234561https://www.ncbi.nlm.nih.gov/pubmed/41375158https://doi.org/10.1002/anie.201704798https://www.ncbi.nlm.nih.gov/pubmed/28670864https://doi.org/10.1039/d1tc02344fhttps://doi.org/10.1107/s0108768190011041https://doi.org/10.1016/j.solidstatesciences.2005.02.011https://doi.org/10.1021/ic990921ehttps://www.ncbi.nlm.nih.gov/pubmed/12526369https://doi.org/10.1088/1742-6596/325/1/012002https://doi.org/10.2109/jcersj2.121.287https://doi.org/10.4028/www.scientific.net/msf.321-324.198https://doi.org/10.3390/inorganics14070174 Introduction  Results and Discussion  Materials and Methods  Conclusions  References