12306 | J. Mater. Chem. C, 2019, 7, 12306--12311 This journal is©The Royal Society of Chemistry 2019

Cite this: J.Mater. Chem. C, 2019,

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Predicted polymorph manipulation in an exoticdouble perovskite oxide†

He-Ping Su,a Shu-Fang Li,*b Yifeng Han, b Mei-Xia Wu,b Churen Gui,c

Yanfen Chang,d Mark Croft,e Steven Ehrlich,f Syed Khalid,f Umut Adem,g

Shuai Dong,c Young Sun,d Feng Huang h and Man-Rong Li *b

Predicted polymorph manipulation offers a cutting-edge route to design function-oriented materials in an

exotic double perovskite-related oxide A2BB0O6 with small A-site cations. Herein, first-principles density

functional theory calculations in light of the equation of state for solid, for the first time, was used to predict

the Mg3TeO6 (R%3)-to-perovskite (P21/n) type phase transition in Mn3TeO6 at around 5 GPa, regardless of the

deployment of magnetic interactions. The high-pressure synthesis and synchrotron diffraction crystal

structure analysis corroborated experimentally the polymorph variation in Mn22+Mn2+Te6+O6, which was

accompanied by a 13 K increase in the antiferromagnetic ordering temperature (37 K) in the high-pressure

perovskite polymorph compared to that of the ambient-pressure R%3 phase (24 K). The magnetodielectric

coupling remains up to 50 K with the maximum being around the magnetic ordering temperature in the

perovskite Mn3TeO6. Thus, the predicted polymorph manipulation here offers the possibility of discovering

accelerated materials by inverse design in exotic perovskite oxides.

Pressure-driven polymorph evolution is a pre-eminent strategyfor property-oriented material design,1,2 as it has been extensivelyapplied to achieve the desired function in an exotic perovskite-related ABO3 and A2BB0O6 oxides with small A-site cations.3–11 Forexample, the multiferroic LiNbO3-type (R3c) ScFeO3 and FeTiO3 canbe achieved at 6 and 12 GPa from their ambient-pressure (AP)bixbyite (Ia%3) and ilmenite (R%3) precursors, respectively,3,4,6 and theperovskite (Pnma) polymorph of MnVO3 (a type-II multiferroics) canbe synthesized from its lower-pressure (3 GPa) ilmenite analogabove 5 GPa.7 Practical magnetoelectricity has also been discoveredin compounds with enhanced magnetic interactions in thetransition-metal-only perovskite-related phases such as Mn2FeMO6

(M = Mo,9 Re10,11) prepared at high pressure (HP). However, so far,

the pressure-dependent polymorph modification of the exoticperovskites is still a high-cost and low-efficient trial-and-errorprocess, largely due to their undistinguishable values of thegeometrical descriptors like the perovskite-related tolerance factor(t).12 Thus, there is not yet any universal rule to precisely govern orpredict the polymorphs of a given composition. Recently, first-principles density functional theory (DFT) calculations of the totalenergy based on the equations of state13,14 have shed light on thestructure prediction of simple ABO3 exotic perovskites, as proposedin the pressure-induced LiSbO3-to-LiNbO3 transition in LiSbO3,15

and ilmenite-perovskite-LiNbO3 conversion in ZnTiO3,16 in whichthe calculated results established pressure-dependent phasestability maps of each polymorph candidate (ilmenite, perovskite,LiNbO3, and LiSbO3) for LiSbO3 and ZnTiO3, and well explained theexperimentally observed phase evolution. These findings suggestedthe possible structure prediction of the exotic perovskite oxides byestimating the total energy of the polymorph candidate.

In the non-magnetic simple ABO3-system, such as LiSbO3

and ZnTiO3, the image is more clear than in double A2BB0O6-system, where the increased diversity of the cationic arrange-ments yield six possible polymorphs, reported to date, namely,distorted GdFeO3-type double perovskites (P21/n), B-site orderedLiSbO3 derivatives (Pnn2), Mg3TeO6 (R%3), corundum derivatives(ordered ilmenite or Ni3TeO6 type R3), bixbyite (Ia%3), and b-Li3VF6

(C2/c) (Fig. 1). Further complexity also arises from the multi-dimensional competition in the magnetic A2BB0O6-system.17

Thus, the ability to precisely predict and manipulate polymorphsrequires the understanding of interplays between the macroscopic

a School of Physics, Sun Yat-Sen University, Guangzhou 510275, P. R. Chinab Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education,

School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, P. R. Chinac School of Physics, Southeast University, Nanjing 211189, Chinad Beijing National Laboratory for Condensed Matter Physics, Institute of Physics,

Chinese Academy of Sciences, Beijing 100190, P. R. Chinae Department of Physics and Astronomy, Rutgers, The State University of New Jersey,

Piscataway, NJ 08854, USAf NSLS-II, Brookhaven National Laboratory, Upton, NY 11973, USAg Department of Materials Science and Engineering, Izmir Institute of Technology,

Urla 35430, Izmir, Turkeyh School of Materials, Sun Yat-Sen University, Guangzhou 510275, P. R. China.

E-mail: limanrong@mail.sysu.edu.cn

† Electronic supplementary information (ESI) available. CCDC 1912424 and1912425. For ESI and crystallographic data in CIF or other electronic formatsee DOI: 10.1039/c9tc03367j

Received 22nd June 2019,Accepted 10th September 2019

DOI: 10.1039/c9tc03367j

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(synthesis conditions) and microscopic (electronic spin, charge,orbital structures, and lattice) factors. To the best of our knowledge,so far, no such research work has been reported with regards tothe use of magnetically active exotic double perovskite-relatedA2BB0O6 compounds to elucidate the contribution of magneticinteractions in the polymorph prediction.

In this work, we present for the first time the predictedpolymorph manipulation in exotic double perovskite-relatedMn3TeO6 (MTO), and studied its crystal structure evolution andthe accompanied physical property variation.

AP-prepared A3TeO6 showed very similar t, but adopted fourpossible structural types (Fig. 1): Mg3TeO6-type (R%3) for A = Mg(t = 0.822)18 and Mn (t = 0.836);19 b-Li3VF6-type (C2/c) for A = Co(t = 0.822)20 and Zn (t = 0.823);21 polar corundum (R3) inNi3TeO6 (t = 0.819);22 and bixbyite in Cu3TeO6 (t = 0.816),23

providing an ideal platform to understand the polymorphmodification. The AP-MTO was found to be isostructural withthe rhombohedral (R%3) Mg3TeO6, as illustrated in Fig. S1 and S2(ESI†), which displays the antiferromagnetic (AFM) type-IImultiferroic behavior.24 To investigate the structure variationof MTO under pressure, the first-principles DFT calculations, inlight of the equation of state for solid, were conducted in threemost probable polymorphs, namely, R%3 (AP-MTO in Mg3TeO6),R3 (polar corundum Ni3TeO6-type), and P21/n (distortedGdFeO3-type perovskite). Chemically and geometrically, the sizeand charge difference between Mn2+ (the ionic radius inoctahedral(VI) coordination VIr = 0.83 Å) and Te6+ (VIr = 0.56 Å)energetically did not favor the formation of bixbyite Ia %3,LiSbO3-derived Pnn2, or b-Li3VF6-type C2/c (Section 2.2 ofESI†), and thus, they were not considered in the calculations.

Fig. 2 shows the variation of relative enthalpies, volume, andtotal energy for the three types of MTO phases.13 Further, theenthalpy of AP-MTO was observed to be the lowest under lower-pressure conditions, while the P21/n-type structure becamemore stable at higher pressure (Fig. 2a). Moreover, the volumeof P21/n-type HP-MTO was estimated to be the smallest underpressure (Fig. 2b). The phase transition, which occurred atB5 GPa indicated that the R3-type MTO was less stable thanthe P21/n-type HP-MTO, and hence the AP-MTO can directlytransform into P21/n-type HP-MTO.

This conversion pressure of B5 GPa coincided well withthe experimental results, as the synthesis at 5 GPa yielded aP21/n-type polymorph. Obviously, the polar R3 state does notappear throughout the whole calculations from the energic pointof view. Therefore, the quantitative results (the DH or the criticalpressure shown in Fig. 2a) could change slightly with variouscalculation parameters, such as the Coulomb repulsion U

Fig. 1 Possible crystal structure types of A2BB0O6 with small A site cations,including distorted GdFeO3-type double perovskites (P21/n), B-siteordered LiSbO3 derivatives (Pnn2), Mg3TeO6 (R %3), corundum derivatives(LiNbO3-type R3c, ilmenite R %3, and ordered ilmenite or Ni3TeO6 type R3),bixbyite (Ia %3), and b-Li3VF6 (C2/c).

Fig. 2 The pressure dependencies of the relative enthalpies (a), volume(b), and energy (c) for Mg3TeO6 (R %3), double perovskite (P21/n), and polarcorundum (R3) types of Mn3TeO6.

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(Table S1, ESI†), but the overall qualitative trends in thestructure were steady. Additionally, the effect of Dzyaloshinskii–Moriya (DM) interaction for different proposed ferromagnetic/antiferromagnetic (FM/AFM) spin structures did not confoundthe overall results; therefore, in order to focus on the pressureeffect on the structure, the simplest FM order was adopted in allcalculations by ignoring the energy shift that complex magneticorders may undergo.

The HP-MTO polymorph was observed to adopt a typicalmonoclinic (P21/n) double perovskite structure, synthesized at5 GPa between 1173–1273 K, following the prediction in Fig. 2,with subsequent refinement using the SPXD data, as shown inFig. 3. Attempts to synthesize the HP-MTO phase below 5 GPa/1173 K were unsuccessful and yielded either the AP phase or amixture of both polymorphs (Fig. S3, ESI†). Moreover, the densepolycrystalline pellets and small single crystals (B20 mm) of theHP phase can be obtained at 1173 and 1273 K, respectively,which presented the identical PXD patterns. Therefore, thedetailed crystal structure analyses were conducted using bothpowder and single-crystal diffraction methods. The finalrefined crystallographic parameters and agreement factors arelisted in Table S2 (ESI†). Additionally, the selected interatomicdistances, bond angles, and bond valence sum (BVS) calcula-tions are listed in Table S3 (ESI†).

Because the crystallographic data from SPXD and single-crystaldiffraction approaches were almost identical within the estimatedstandard deviation, the results from SPXD in Tables S2 and S3(ESI†) were used to discuss the crystal structure of HP-MTO, giventhe higher resolution of synchrotron beamline. The crystalstructure of HP-MTO (P21/n) (No. 14), in which a = 5.2945(1) Å,b = 5.4527(1) Å, c = 7.8092(1) Å, b = 90.37(1)1, V = 225.44 (1) Å3,Z = 2, Rwp = 9.96%, and Rp = 6.50%, is shown in the insetof Fig. 3, and is isostructural with other Mn2BB0O6 doubleperovskites.10,11,25–33 It was also observed that the structure

consisted of Mn1O8 coordination and rock-salt ordering ofMn2O6 and TeO6 octahedra. The average hMn1–Oi bond length(2.425(1) Å) was in line with those of the A-site hMn–Oi inisostructural Mn2BB0O6 varying between 2.379 and 2.406 Å.10,26,29,33

The hMn2–Oi of 2.175(1) Å was somewhat longer than that of theB-site Mn2+/3+ (2.138(1) Å) in the isostructural Mn2MnReO6,28

which was reasonable upon considering the ionic size differencebetween Mn2+ and Mn3+.34 The TeO6 octahedron was found to bemore regular with the Te–O distance between 1.916(1) and1.967(1) Å. Comparison of the structural parameters with the parentanalogs suggested formal oxidation states of Mn2

2+Mn2+Te6+O6 ofthe HP perovskite polymorph, as further corroborated by the BVScalculations (Table S3, ESI†) and XANES analysis discussed inFig. S4 and Section 2.1 of ESI.†

The HP synthesis could enhance the steric atomic inter-actions and induce transformation to denser structures withhigher internal energy (Fig. 2c) related to the thermodynamicstability.35–37 When heated at AP, an HP-phase can eitherdecompose or revert back to the AP-phase. For example, therecently reported LiSbO3-derived HP-Li2GeTeO6 (orthorhombicPnn2, prepared at 3–5 GPa and 1073 K) can persist up to 843 Kat AP before fully converting back to the AP-ordered ilmenite(R3) analog, accompanied by cell volume expansion anddecreasing density from 5.23 to 4.97 g cm�1.37 Similarly, theperovskite polymorph of Mn2CrSbO6 (P21/n, prepared at 8 GPaand 1473 K) underwent a phase transition to ilmenite (R%3) afterthermal treatment at 973 K.27 Fig. 4 presents the room-temperature PXD patterns of the HP-MTO (5 GPa and 1273 Kproduct) after annealing at variable temperatures. It can beseen that the P21/n phase persisted up to 823 K, and convertedback to the AP-MTO above 873 K.

The temperature-dependent susceptibilities for HP-MTOmeasured in the field of H = 1000 Oe are shown in Fig. 5a.

Fig. 3 Rietveld refinements from the SPXD data of HP-MTO prepared at5 GPa and 1173 K in GdFeO3-type distorted monoclinic structure (P21/n).Inset shows the perspective polyhedral view of the unit cell structure alongc direction. Mn2O6, green; TeO6, yellow; Mn1, green spheres; and O, redspheres.

Fig. 4 Room-temperature PXD patterns of HP-MTO after annealing itfrom 300 to 1023 K in Ar for 30 min at each temperature point. The PXDpatterns of the AP-MTO are plotted on the top for comparison. Therelative intensity variation of the patterns after being annealed in thetemperature range of 300–873 K, owing to the preferred orientation.

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The ZFC (zero-field cooling) and FC (field cooling) curvesexhibited typical AFM behavior with Neel temperature TN of37 K. The Curie–Weiss (CW) temperature yCW from the fit tow(T) = C/(T � yCW) converged to �193.98 K, indicating that theinteractions in HP-MTO were dominated by AFM, as furtherevidenced by the isothermal M(H) curves in Fig. 5b. Furthermore,the effective magnetic moment meff of 10.23 mB f.u.�1 (formula unit)indicated a S = 5/2 high-spin state of Mn2+ (meff(Mn2+) B 5.89 mB) asevidenced by the crystal structure and XANES results. Fortemperatures below about 130 K, the w(T) deviated clearly fromthe CW behavior, suggesting that the short-range correlationsstarted to develop, as manifested by the slightly indicativehysteresis in Fig. 5b. Compared with the AP-MTO (AFM orderingbelow 24 K),38 the HP-MTO becomes ordered at a highertemperature, as suggested by the sharp peak at 37 K in Fig. 5a.

At low temperatures, a relatively sharp peak was observed at34.9 K in the heat capacity curve, as shown in the inset ofFig. 5a, which echoes the AFM transition detected in themagnetic susceptibility measurements. This latter determina-tion of the Neel temperature was more accurate than themagnetic measurements, as closer data points were recordedin the heat capacity measurements.

Temperature dependence of the dielectric constant for theHP-MTO sample showed an anomaly at TN = 34.6 K (Fig. 6),whereas no anomaly could be detected in the temperaturedependence of dielectric loss. This anomaly in e around TN B35.7 K demonstrated the presence of magnetodielectric couplingin HP-MTO. The temperature of this anomaly shifted with anincrease in the frequency. Therefore, dielectric relaxation effectscan be ruled out. At the highest measurement frequency of1 MHz, the dielectric constant increased with respect to themeasurements at lower frequencies. This kind of increase in thedielectric constant, at high frequencies, typically results fromthe inductive contribution of the measurement leads. However,this weak anomaly at TN was not a divergent peak, suggesting theabsence of ferroelectric order below TN. In agreement with thisconclusion, no detectable pyroelectric response was observedfrom the polycrystalline HP-MTO.

Apparently, the HP-MTO crystallized in a centrosymmetricspace group P21/n, and unlike in the parent R%3 AP-MTO,39 themagnetic order in HP-MTO was probably not cycloidal and/orhelical, and does not induce ferroelectricity. Generally, theconfirmation of the absence of ferroelectricity requires neutrondiffraction experiments and further measurements on single-crystal samples, which are planned as future work. Applicationof the magnetic field slightly increased the dielectric constantand shifted the dielectric anomaly at the magnetic orderingtemperature to slightly lower temperatures, as shown in theinset of Fig. 6. Additionally, the maximum magnetodielectriccoupling occurred near the magnetic ordering temperature,and the magnetodielectric effect remained up to about 50 K.

Conclusions

In summary, the polymorph manipulation by the computa-tional prediction of the relative energetics of competing phaseshas been, for the first time, observed in an exotic double

Fig. 5 (a) The temperature-dependent susceptibility and (inset) inversesusceptibility of the HP-MTO measured from 5 K to 380 K under magneticfield of 1000 Oe. (b) Isothermal magnetization measured at 5 and 40 K,respectively.

Fig. 6 Maximum magnetodielectric coupling occurs near the magneticordering temperature, with the magnetodielectric effects persisting up toabout 50 K.

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perovskite with small A-site cations. A pressure-induced Mg3TeO6

(R%3) to double perovskite (P21/n) type phase transition was predictedto occur around 5 GPa in Mn3TeO6, which was further manifestedby an experimental synthesis and crystallographic analysis. Thispolymorph conversion was accompanied by about 15 K higherantiferromagnetic ordering temperature and magnetodielectriccoupling in the perovskite phase. The predicted polymorphmanipulation in Mn3TeO6, for the first time, builds a connectionbetween Mg3TeO6 and double perovskite polymorphs, thusbroadening the platform for structure modulation in A2BB0O6.It is also shown that the energetic effect of different magneticstructures may not be so critical in polymorph prediction in lightof the equation of state for solids, as the energy contributionfrom the DM interaction does not dominate the ground states ofthe competing polymorphs. Thus, these findings will help toaccelerate the discovery of new materials via data mining andhigh-throughput calculations in exotic A2BB0O6 (more than13 000 new compounds by estimation under charge balance),and are of great interest for the in-depth study of magneticmaterials or to access preparation methods and properties ofmultifunctional materials.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was financially supported by the National ScienceFoundation of China (NSFC-21801253, 11804404, and 21875287).Work at Brookhaven National Laboratory was supported by theDOE BES (DE-SC0012704) on the NSLS-II Beamline 7BM and onNSLS-I on the X19A. The authors thank beamline BL14B1(Shanghai Synchrotron Radiation Facility) for providing thebeam time and helps during experiments. The authors wouldlike to thank Prof. David Walker at LDEO in Columbia Universityfor enlightening discussions.

Notes and references

1 Y. Hamasaki, T. Shimizu, S. Yasui, T. Taniyama, O. Sakataand M. Itoh, Cryst. Growth Des., 2016, 16, 5214–5222.

2 R. Ramesh and D. G. Schlom, Nat. Rev. Mater., 2019, 4,257–268.

3 T. Kawamoto, K. Fujita, I. Yamada, T. Matoba, S. J. Kim, P. Gao,X. Pan, S. D. Findlay, C. Tassel, H. Kageyama, A. J. Studer,J. Hester, T. Irifune, H. Akamatsu and K. Tanaka, J. Am. Chem.Soc., 2014, 136, 15291–15299.

4 M.-R. Li, U. Adem, S. R. C. McMitchell, Z. Xu, C. I. Thomas,J. E. Warren, D. V. Giap, H. Niu, X. Wan, R. G. Palgrave,F. Schiffmann, F. Cora, B. Slater, T. L. Burnett, M. G. Cain,A. M. Abakumov, G. van Tendeloo, M. F. Thomas, M. J.Rosseinsky and J. B. Claridge, J. Am. Chem. Soc., 2012, 134,3737–3747.

5 Y. Inaguma, M. Yoshida and T. Katsumata, J. Am. Chem.Soc., 2008, 130, 6704–6705.

6 T. Varga, A. Kumar, E. Vlahos, S. Denev, M. Park, S. Hong,T. Sanehira, Y. Wang, C. Fennie, S. Streiffer, X. Ke, P. Schiffer,V. Gopalan and J. Mitchell, Phys. Rev. Lett., 2009, 103, 047601.

7 M. Markkula, A. M. Arevalo-Lopez, A. Kusmartseva, J. A.Rodgers, C. Ritter, H. Wu and J. P. Attfield, Phys. Rev. B: Condens.Matter Mater. Phys., 2011, 84, 094450.

8 J. Cong, K. Zhai, Y. Chai, D. Shang, D. D. Khalyavin, R. D.Johnson, D. P. Kozlenko, S. E. Kichanov, A. M. Abakumov, A. A.Tsirlin, L. Dubrovinsky, X. Xu, Z. Sheng, S. V. Ovsyannikov andY. Sun, Nat. Commun., 2018, 9, 2996.

9 M.-R. Li, M. Retuerto, D. Walker, T. Sarkar, P. W. Stephens,S. Mukherjee, T. S. Dasgupta, J. P. Hodges, M. Croft, C. P.Grams, J. Hemberger, J. Sanchez-Benıtez, A. Huq, F. O. Saouma,J. I. Jang and M. Greenblatt, Angew. Chem., Int. Ed., 2014, 53,10774–10778.

10 M.-R. Li, M. Retuerto, Z. Deng, P. W. Stephens, M. Croft,Q. Huang, H. Wu, X. Deng, G. Kotliar, J. Sanchez-Benıtez,J. Hadermann, D. Walker and M. Greenblatt, Angew. Chem.,Int. Ed., 2015, 54, 12069–12073.

11 A. M. Arevalo-Lopez, G. M. McNally and J. P. Attfield, Angew.Chem., Int. Ed., 2015, 54, 12074–12077.

12 M. W. Lufaso and P. M. Woodward, Acta Crystallogr., Sect. B:Struct. Sci., 2001, 57, 725–738.

13 F. D. Murnaghan, Proc. Natl. Acad. Sci. U. S. A., 1944, 30,244–247.

14 C. Collins, M. S. Dyer, A. Demont, P. A. Chater, M. F. Thomas,G. R. Darling, J. B. Claridge and M. J. Rosseinsky, Chem. Sci.,2014, 5, 1493–1505.

15 Y. Inaguma, A. Aimi, D. Mori, T. Katsumata, M. Ohtake,M. Nakayama and M. Yonemura, Inorg. Chem., 2018, 57,15462–15473.

16 Y. Inaguma, A. Aimi, Y. Shirako, D. Sakurai, D. Mori,H. Kojitani, M. Akaogi and M. Nakayama, J. Am. Chem.Soc., 2014, 136, 2748–2756.

17 D. Yi, N. Lu, X. Chen, S. Shen and P. Yu, J. Phys.: Condens.Matter, 2017, 29, 443004.

18 G. Blasse and W. Hordijk, J. Solid State Chem., 1972, 5, 395–397.19 H. Singh, A. K. Sinha, H. Ghosh, M. N. Singh, P. Rajput,

C. L. Prajapat, M. R. Singh and G. Ravikumar, J. Appl. Phys.,2014, 116, 074904.

20 H. Singh, H. Ghosh, T. V. Chandrasekhar Rao, G. Sharma,J. Saha and S. Patnaik, J. Appl. Phys., 2016, 119, 044104.

21 M. Weil, Acta Crystallogr., Sect. E: Struct. Rep. Online, 2006,62, i246–i247.

22 J. W. Kim, S. Artyukhin, E. D. Mun, M. Jaime, N. Harrison,A. Hansen, J. J. Yang, Y. S. Oh, D. Vanderbilt, V. S. Zapf andS. W. Cheong, Phys. Rev. Lett., 2015, 115, 137201.

23 X. Zhu, Z. Wang, X. Su and P. M. Vilarinho, ACS Appl. Mater.Interfaces, 2014, 6, 11326–11332.

24 M. Weil, Acta Crystallogr., Sect. E: Struct. Rep. Online, 2006,62, i244–i245.

25 E. Solana-Madruga, A. J. Dos santos-Garcia, A. M. Arevalo-Lopez, D. Avila-Brande, C. Ritter, J. P. Attfield and R. Saez-Puche, Dalton Trans., 2015, 44, 20441–20448.

Journal of Materials Chemistry C Paper

Publ

ishe

d on

11

Sept

embe

r 20

19. D

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2019

5:5

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This journal is©The Royal Society of Chemistry 2019 J. Mater. Chem. C, 2019, 7, 12306--12311 | 12311

26 G. V. Bazuev, A. P. Tyutyunnik, M. V. Kuznetsov and Y. G.Zainulin, J. Supercond. Novel Magn., 2018, 31, 2907–2914.

27 A. J. Dos santos-Garcia, E. Solana-Madruga, C. Ritter,D. Avila-Brande, O. Fabelo and R. Saez-Puche, Dalton Trans.,2015, 44, 10665–10672.

28 A. M. Arevalo-Lopez, F. Stegemann and J. P. Attfield, Chem.Commun., 2016, 52, 5558–5560.

29 M.-R. Li, J. P. Hodges, M. Retuerto, Z. Deng, P. W. Stephens,M. C. Croft, X. Deng, G. Kotliar, J. Sanchez-Benıtez, D. Walkerand M. Greenblatt, Chem. Mater., 2016, 28, 3148–3158.

30 A. J. D. Santos-Garcıa, C. Ritter, E. Solana-Madruga andR. Saez-Puche, J. Phys.: Condens. Matter, 2013, 25, 206004.

31 R. Mathieu, S. A. Ivanov, I. V. Solovyev, G. V. Bazuev, P. AnilKumar, P. Lazor and P. Nordblad, Phys. Rev. B: Condens.Matter Mater. Phys., 2013, 87, 014408.

32 A. P. Tyutyunnik, G. V. Bazuev, M. V. Kuznetsov and Y. G.Zainulin, Mater. Res. Bull., 2011, 46, 1247–1251.

33 M.-R. Li, P. W. Stephens, M. Croft, Z. Deng, W. Li, C. Jin,M. Retuerto, J. P. Hodges, C. E. Frank, M. Wu, D. Walkerand M. Greenblatt, Chem. Mater., 2018, 30, 4508–4514.

34 R. Shannon, Acta Crystallogr., Sect. A: Cryst. Phys., Diffr.,Theor. Gen. Crystallogr., 1976, 32, 751–767.

35 G. Liu, J. Gong, L. Kong, R. D. Schaller, Q. Hu, Z. Liu, S. Yan,W. Yang, C. C. Stoumpos, M. G. Kanatzidis, H.-K. Mao andT. Xu, Proc. Natl. Acad. Sci. U. S. A., 2018, 115, 8076.

36 Z. Gao, Y. Liu, C. Lu, Y. Xia, L. Fang, Y. Ma, Q. He, D. He andS. Yang, J. Am. Ceram. Soc., 2018, 101, 2571–2577.

37 M. H. Zhao, W. Wang, Y. Han, X. Xu, Z. Sheng, Y. Wang,M. Wu, C. P. Grams, J. Hemberger, D. Walker, M. Greenblattand M. R. Li, Inorg. Chem., 2019, 58, 1599–1606.

38 R. Mathieu, S. A. Ivanov, P. Nordblad and M. Weil, Eur. Phys.J. B, 2013, 86, 1–4.

39 L. Zhao, Z. Hu, C.-Y. Kuo, T.-W. Pi, M.-K. Wu, L. H. Tjengand A. C. Komarek, Phys. Status Solidi RRL, 2015, 9, 730–734.

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1

Supporting Information

Predicted Polymorph Manipulation in Exotic Double

Perovskite Oxide

He-Ping Su,a Shu-Fang Li,b,* Yi-Feng Han,b Mei-Xia Wu,b Churen Gui,c Yanfen

Chang,d Mark Croft,e Steven Ehrlich,f Syed Khalid,f Umut Adem,g Shuai Dong,c Young

Sun,d Feng Huang,h Man-Rong Lib,*

aSchool of Physics, Sun Yat-Sen University, Guangzhou 510275, P. R. China

bKey Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education,

School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, P. R. China

cSchool of Physics, Southeast University, Nanjing 211189, China

dBeijing National Laboratory for Condensed Matter Physics, Institute of Physics,

Chinese Academy of Sciences, Beijing 100190, P. R. China

eDepartment of Physics and Astronomy, Rutgers, The State University of New Jersey,

Piscataway, NJ 08854, USA

fNSLS-II, Brookhaven National Laboratory, Upton, NY 11973, USA

gDepartment of Materials Science and Engineering, İzmir Institute of Technology, Urla

35430, İzmir, Turkey

hSchool of Materials, Sun Yat-Sen University, Guangzhou 510275, P. R. China

Email: limanrong@mail.sysu.edu.cn

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry C.This journal is © The Royal Society of Chemistry 2019

2

Table of Contents1. Experimental Procedures 2

1.1 Computational Descriptions. 2

1.2 Synthesis. 2

1.3 Powder and Single Crystal X-ray Diffraction. 2

1.4 X-ray Absorption Near Edge Spectroscopy. 2

1.5 Magnetic and Magnetodielectric Properties Measurements. 2

2. Results and Discussion 3

2.1 Mn-K XANES. 3

2.2 Polymorphs of A2BB’O6 with small A-site cations. 3

3. Graphics and Supporting Data 4

4. References 8

1. Experimental Procedures1.1. Computational Descriptions.

To investigate the crystal structure evolution of MTO with increasing pressures, first-

principles calculations based on density functional theory (DFT) were performed with the PBE-

sol exchange correlation functional as implemented in Vienna ab-initio Simulation Package

(VASP).1, 2 The plane wave cutoff energy is set as 520 eV and the integrations in the Brillouin

zone were performed with 4×4 ×3 γ-centered k-point mesh. Considering the strong correlation

of the partially filled d shell of the Mn ion, an on-site Coulomb repulsion U was set using the

Dudarev implementation.3 Different U (3 and 4 eV) in the R-3 state have been tested for the U-

dependence, which leads to a conclusion that U = 3 eV is the better choice. In fact, the results

of different U shift insignificantly (Table S1). Different simplest

ferromagnetic/antiferromagnetic order modes were adopted in all calculations by ignoring the

energy shift that complex magnetic orders may lead to.

1.2 Synthesis.

Mg3TeO6-type MTO phase (rhombohedral R-3, denoted as AP-MTO) was synthesized by

a conventional solid-state reaction using the following starting materials: MnO (99.99%, Alfa

Aesar), Mn2O3 (99.99%, Sigma Aldrich), and TeO2 (99.99%, Alfa Aesar). Stoichiometric

mixtures of the starting materials were pelletized and heated in Ar at 1023 K for 24 h (heating

and cooling rate of 5 K/min) with intermediate grinding as reported previously (Fig. S1).4-7

Then the as-made AP-MTO precursor was loaded into a graphite heater lined with Pt capsule

3

inside an MgO crucible, followed by heating between 1173-1273 K at 5 GPa for 30 min in a

Walker-type multi anvil press to prepare the HP phase (hereafter denoted as HP-MTO) as in

our previous work.8-14 Finally, the specimen was quenched to room temperature by tuning off

the voltage supply to the resistance furnace. The pressure was maintained during the

temperature quenching and slowly (typically within 8-12 h) decompressed to ambient.

1.3 Powder and Single Crystal X-ray Diffraction.

Both the AP and HP products were initially characterized by laboratory powder X-ray

diffraction (PXD, Bruker D8 ADVANCE, Cu Kα, λ = 1.5418 Å) for phase identification and

purity examination. Synchrotron powder X-ray diffraction (SPXD) data were collected at

ambient condition on the beamline BL14B (λ = 0.68800 Å) at the Shanghai Synchrotron

Radiation Facility (SSRF). The sample is loaded into a 0.5 mm glass capillary and the

diffraction data were collected in spinning-mode. Mythen1K detector was used for high quality

data acquisition and the wavelength (λ = 0.6895728 Å) was obtained using LaB6 standard. The

detailed information about beamline BL14B1 can be found in references.15, 16 The SPXD data

and crystal structure were analyzed and refined with the TOPAS-Academic V6 software

package.17 Single crystal of the HP-MTO was mounted on a glass fiber for single-crystal XRD

analysis. The measurements were performed on a SuperNova diffractometer equipped with

graphite-monochromated Mo−Kα radiation (λ = 0.71073 Å) at 293 K. The intensity data sets

were collected with a ω-scan technique and reduced using CrystalClear software.18 The

structure of HP-MTO was computed through direct methods and refined using full-matrix least-

squares techniques on F2, with anisotropic thermal parameters for all atoms. All of the

calculations were performed with the SHELXL 2013 package of crystallographic software.19

The formulas collectively consider the crystallographically refined compositions and the

requirements of charge neutrality.

1.4 X-ray Absorption Near Edge Spectroscopy.

Mn-K X-ray absorption near edge spectroscopy (XANES) data were collected in both the

transmission and fluorescence mode with simultaneous standards. All of the spectra were fit to

linear pre- and post-edge backgrounds and normalized to unity absorption edge step across the

edge.20-24 The title compound XANES spectra were collected at the QAS, 7BM Beamline at

NSLS-II using a Si(111) channel-cut monochromator in the “quick”, continuous scanning

mode. Some of the standard spectra were previously collected on beam line X-19A at NSLS-I

with a Si-111 double crystal monochromator.

1.5 Magnetic and Magnetodielectric Properties Measurements.

Magnetization and magnetodielectric response were measured on a commercial Physical

4

Property Measurement System (PPMS). The magnetic susceptibility was measured in zero-field

cooled (ZFC) and field cooled (FC) conditions under a 0.1 T magnetic field, for temperatures

ranging from T = 5 to 300 K. Specific heat measurements between 10 and 60 K were also

performed. To measure the dielectric constant, electrodes made of silver paste were painted on

the widest faces of samples. The dielectric response was measured in a Cryogen-free

Superconducting Magnet System (Oxford Instruments, Teslatron PT) using an LCR meter

(Agilent E4980A) at frequencies of 1, 10, 100, and 1000 kHz.

2. Results and Discussion2.1. Mn-K XANES.

XANES measurements of the K-edges of 3d row transition metals in compounds has

proven to be a useful probe of the transition metal valence/configuration.20-24 These edges are

dominated by peak-like 1s to 4p transitions and typically exhibit a chemical shift to higher

energies with increasing transition metal valance. Here the chemical shift can be monitored

either by the energy of the peak or the rapidly-rising-portion of the near edge spectra. Referring

to Fig. S4a the chemical shift of the peak-energy (indicated by the label “b”) downward

between CaMn4+O3, LaMn3+O3, and Sr2Mn2+ReO6 standards is quite clear. The Ba2Mn2+ReO6

spectrum illustrates how the main peak can be split into two components (b1/b2 in Fig.S4a),

respectively shifted up (down) in energy but with the centrum of the split-peak feature lying in

the Mn2+ energy range.20, 22-24 A similar splitting is manifested in the Mn2+O spectrum.23 Note

also that the Mn2+ standard spectra also typically manifest a prominent a-feature (see Fig. S4a

top) below the energy of the b-peak features.

The Mn-K main edges of HP-MTO and the isostructural Mn2FeReO6 are superimposed in

Fig. S4a. It should be noted that the spectral peak of the Mn2+, distorted perovskite-A-site, in

the latter spectrum, is noticeably shifted to lower energy (see line “2” in figure) relative to the

peaks in the other Mn2+ spectra,24 but is still consistent with the divalent assignment. The HP-

MTO spectrum is consistent with two Mn2+, A-sites, similar to Mn2FeReO6, and one Mn2+ B-

site, similar to Ba2Mn2+ReO6. Specifically, the Mn2+ B-site contributes the following spectral

features: the sharp, split b1/b2 peaks at the vertical lines labeled 2/3; and the clear excess

intensity at the position labeled by the 1-line which falls at the energy expected for an a-feature

(noted above). Note that both the A-site and B-site make contributions in the vicinity of the line

labeled 1 in the figure.

The pre-edge portion of the Mn-K spectra are shown in Fig. S4b. Such pre-edge spectral

features involve quadrupole, and d/p-hybridization induced dipole, transitions into final d-

5

states.21, 24 Again, an increasing-valence/chemical-shift-to-higher-energy is typically seen in the

pre-edge features, along with changes in the spectral distribution. Comparison of the HP-MTO

pre-edge feature to those of the standard compounds further supports the Mn2+ assignment for

this compound. Thus, both the main-edge and pre-edge Mn K results support a Mn2+ state for

the A- and B- sites in HP-MTO.

2.2. Polymorphs of A2BB’O6 with small A-site cations.

A2BB’O6 compounds with small A-site cation, where the ionic radius of A is no larger than

that of the high spin (HS) Mn2+, can adopt a number of structure types.25-29 These are distorted

GdFeO3-derived (monoclinic P21/n) double perovskite, corundum derivatives (LiNbO3-type

R3c, ilmenite R-3, ordered ilmenite, or Ni3TeO6 type R3), LiSbO3 derivatives (B-site ordered,

Pnn2), Mg3TeO6 (R-3), bixbyite (Ia-3), and β-Li3VF6 (C2/c) as shown in Fig. 1. So far, the

well-known double-perovskites (AO8 in framework of rock-salt ordering BO6 and B’O6) have

only been reported in Mn2BB’O6 (B = Sc,30 V,31 Cr,32 Mn,9, 33 Fe,10, 34-37 B’ = Sb,30-32, 34-36 Re;9,

10, 33, 37 and B = Fe0.8Mo0.2,38 B’ = Mo38). The corundum family can be described as highly

perovskite-related structure considering the very similar BO6 and B’O6 arrangement, regardless

of their face-sharing AO6 counterparts.26 Their crystal structures are mainly dependent on the

cationic ordering degree over the B and B’ sites,39 giving LiNbO3 (R3c) or ilmenite (R-3) type

structure with disordered B/B’, or ordered ilmenite (R3) or Ni3TeO6 (R3) symmetry with

ordered arrangement of B and B’. So far, Li+, Mn2+, Ni2+, and Zn2+ have been predicted or

incorporated into the A-sites of corundum derivatives in Li2BTeO6 (B = Ge,40 Zr, Hf41),

Mn2BB’O6 (B = Mn,42 Fe,11, 13, 14, 43, 44In,45 B’ = Sb,43, 45Nb,14 Ta,14 Mo,13, 44 W11, 42), Ni2BB’O6

(B = Ni,46 Sc, 47 In, 47B’ = Sb, 47 Te46), and Zn2FeB’O6 (B’ = Ta,12 Os48). The LiSbO3 derived

Li2BTeO6 (B = Ge,49 Ti,50 Sn50) possess edge-sharing octahedral chains of alternatively ordered

BO6 and TeO6 with two distinct 6-folded Li atoms zigzagged down the channels. The Mg3TeO6-

type A3TeO6 (A = B = Mg,51-55 Mn4-7, 56), Mn2BSbO6 (B = Sc, In),57 and Sc3CrO658 have

octahedral coordination of all the cation sites with the A and B cations are fully disordered, as

also appears in bixbyite-type Cu2BB’O6 (B = Ga, Mn, Fe, B’ = Sb;59 B = Co,60 Ni,61 Cu,5, 62-70

B’ = Te), In2RuB’O6 (B’ = Mn, Fe),71 and Hg3TeO6,72 in which (A2/3B1/3)O6 and B’O6 are

connected via edge-sharing.72 The β-Li3VF6 structural A3TeO6 (A = Co,4-6, 73-81 Zn82) are not so

common and have the richest cationic arrangement with the coexistence of AO4, AO5, AO6, and

TeO6. The aforementioned diversity of potential structure types of these A2BB’O6 compounds

makes it a challenge to design and identify desired multifunctional materials. Empirically, in

LiSbO3-derived Pnn2 type structure, the charge differences between B and B’ site is no more

than 2 in the known compound, while in In bixbyite Ia-3 structure, the ionic size difference

6

between cations is usually no larger than 0.2 Å. The coexistenc of three, four, five and six

coordination in β-Li3VF6 structure does not favor large ionic radius, especially for the five-

coordinated site, the ionic radius is no more than 0.7 Å in known materials. Therefore,

chemically and geometrically view, Mn2+2Mn2+Te6+O6 does not favor the formation of bixbyite

Ia-3, LiSbO3-derived Pnn2, or β-Li3VF6-type C2/c structure type.

3. Graphics and Supporting Data

Fig. S1 Experimental (top) and simulated (bottom) XRD patterns of the AP-Mn3TeO6, showing

typical Mg3TeO6-type (R-3) phase.

7

Fig. S2 Polyhedral viewing of the crystal structure of AP-Mn3TeO6, which is isotypic with

Mg3TeO6 and can be derived from close packing of strongly distorted hexagonal oxygen layers

parallel to (001), with Mn and two distinct Te atoms in the octahedral interstices. The TeO6

octahedra are very regular, with 3 symmetry, whereas the MnO6 octahedra are considerably

distorted. Both TeO6 octahedra are isolated and share edges with six MnO6 octahedra of edge-

sharing MnO6 pairs. Mn, cyan spheres; O, red spheres; TeO6, yellow.

Fig. S3 Comparison of the PXD patterns of (a) AP-Mn3TeO6 and after treated at (b) 973 K and

3 GPa, (c) 1023 K and 5 GPa, (d) 1123 K and 5 GPa, and (e) 1173 K and 5 GPa.

8

Fig. S4 (a) The Mn-K main-edge of HP-MTO is compared to the edges of a series of standard

compounds with differing formal valence states and local coordination. The overlaid

Mn2+2FeReO6 spectrum has Mn in highly distorted perovskite-A-sites with coordination

reduced to eight-fold (with four short and four long bonds) similar to two of the sites in the title

compound. For clarity, the following octahedrally coordinated standard spectra are presented

vertically displaced upward (downward) for Mn2+ (Mn3+) standards: Mn2+O (with edge

sharing); the B-site (corner sharing) perovskite based CaMn4+O3, LaMn3+O3, Sr2Mn2+ReO6,

and Ba2Mn2+ReO6. Note that the local maximum peaks of the spectra have been labeled b (or

b1/b2 in the cases where a split-peak occurs). A prominent lower energy shoulder in the Mn2+

standards is also labeled “a”. (b) The Mn-K pre-edge of HP-MTO compared to the same series

of standard compounds as in the previous figure. Again, vertical displacement for clarity is

used.

9

Table S1. Comparison of the lattice parameters, magnetic moment, and gap at experimental

and different U values for calculations.

experimental U = 3 eV U = 4 eV

a (Å) 8.8675 8.8809 8.8954b (Å) 8.8675 8.8809 8.8954c (Å) 10.6731 10.7138 10.714Moment (μB/Mn) 4.578 4.615Gap (meV) ~536 ~665

Table S2. Structure parameters for HP-MTO at room temperature refined using SPXD and

single crystal data, respectively.

Atom Site Occ. x y z B/Å2

SPXD

Mn1 4e 1.0 0.0107(1) 0.0475(1) 0.2406(1) 1.230(1)Mn2 2c 1.0 0 0.5 0 0.889(1)Te1 2d 1.0 0.5 0 0 0.761(1)O1 4e 1.0 0.3382(1) 0.3018(1) 0.0831(1) 1.048(1)O2 4e 1.0 0.1946(1) 0.8242(1) 0.0463(1) 1.048(1)O3 4e 1.0 -0.1308(1) 0.4302(1) 0.2706(1) 1.048(1)Monoclinic space group P21/n (No.14), a = 5.2945(1) Å, b = 5.4527(1) Å, c = 7.8092(1) Å,

β = 90.37(1)°, V = 225.44 (1) Å3, Z = 2, Rwp = 9.96%, Rp = 6.50%.

Single crystal

Mn1 4e 1.0 0.0119(1) 0.9530(2) 0.2399(1) 0.05(1)Mn2 2c 1.0 0 0.5 0. 0.04(1)Te1 2d 1.0 0 0.5 0.5 0.03(1)O1 4e 1.0 0.1669(5) 0.2103(5) 0.4178(3) 0.07(1)O2 4e 1.0 0.3007(5) 0.6779(5) 0.4481(3) 0.09(1)O3 4e 1.0 0.1268(5) 0.4240(5) 0.7276(3) 0.05(1)Monoclinic space group P21/n (No.14), Z = 2, a = 5.286(1) Å, b = 5.448(1) Å, c = 7.797(1)

Å, β = 90.37(1)°, V = 224.51 (1)Å3, R1 = 1.69 %, R2 = 1.90 %.

10

Table S3. Selected interatomic distances (Å), bond angles (°) and atomic BVS in HP-MTO at

room temperature using SPXD and single crystal data, respectively.

SPXD

Mn1−O1 2.077(1) Mn2−O2 (×2) 2.077(1)Mn1−O3 2.112(1) Mn2−O3 (×2) 2.187(1)Mn1−O2 2.180(1) Mn2−O2 (×2) 2.261(1)Mn1−O3 2.230(1) (Mn2−O) 2.175(1)Mn1−O1 2.544(1) BVS 2.16Mn1−O2 2.581(1) Te1−O2 (×2) 1.916(1)Mn1−O2 2.728(1) Te1−O3 (×2) 1.953(1)Mn1−O1 2.948(1) Te1−O1 (×2) 1.967(1)(Mn−O) 2.425(1) (Te−O) 1.946(1)BVS 1.90 BVS 5.56

Single Crystal

Mn1−O1 2.132(3) Mn2−O2 (×2) 2.085(3)Mn1−O3 2.144(3) Mn2−O1(×2) 2.193(3)Mn1−O2 2.157(3) Mn2−O3(×2) 2.269(2)Mn1−O3 2.196(3) (Mn2−O)

2.18232.182

Mn1−O1 2.484(3) BVS 2.122Mn1−O2 2.626(3) Te1−O2 (×2) 1.907(3)Mn1−O2 2.679(3) Te1−O1 (×2) 1.920(3)Mn1−O2 2.805(3) Te1−O3 (×2) 1.938(3)(Mn−O) 2.403 (Te−O) 1.922BVS 1.898 BVS 5.928

4. References1. A. R. J. P. Perdew, G. I. Csonka, O. A. Vydrov, G. E. Scuseria, L. A. Constantin, X. Zhou, and K.

Burke, Phys. Rev. Lett., 2007, 136406.2. A. R. J. P. Perdew, G. I. Csonka, O. A. Vydrov, G. E. Scuseria, L. A. Constantin, X. Zhou, and K.

Burke, 2009, 102, 39902.3. G. A. B. S. L. Dudarev, S. Y. Savrasov, C.J. Humphreys, and A.P. Sutton, Phys. Rev. B- Condens.

Matter Mater. Phys, 1998, 57, 1505.4. N. V. Golubko, V. Y. Proidakova, G. M. Kaleva, S. A. Ivanov, A. V. Mosunov, S. Y. Stefanovich, N.

V. Sadovskaya, E. D. Politova and P. Nordblad, Bull. Russ. Acad. Sci. Phys, 2010, 74, 724-726.5. R. Mathieu, S. A. Ivanov, P. Nordblad and M. Weil, Eur. Phys. J. B, 2013, 86, 1-4.6. H. Singh, A. K. Sinha, H. Ghosh, M. N. Singh, P. Rajput, C. L. Prajapat, M. R. Singh and G.

Ravikumar, J. Appl. Phys., 2014, 116, 074904-074901-074904-074909.7. M. Weil, Acta Crystallogr. Sec. E, 2006, 62, i244-i245.

11

8. M.-R. Li, M. Retuerto, P. W. Stephens, M. Croft, D. Sheptyakov, V. Pomjakushin, Z. Deng, H. Akamatsu, V. Gopalan, J. Sánchez-Benítez, F. O. Saouma, J. I. Jang, D. Walker and M. Greenblatt, Angew. Chem. Int. Ed., 2016, 55, 9862-9867.

9. M.-R. Li, J. P. Hodges, M. Retuerto, Z. Deng, P. W. Stephens, M. C. Croft, X. Deng, G. Kotliar, J. Sánchez-Benítez, D. Walker and M. Greenblatt, Chem. Mater., 2016, 28, 3148-3158.

10. M.-R. Li, M. Retuerto, Z. Deng, P. W. Stephens, M. Croft, Q. Huang, H. Wu, X. Deng, G. Kotliar, J. Sánchez-Benítez, J. Hadermann, D. Walker and M. Greenblatt, Angew. Chem. Int. Ed., 2015, 54, 12069-12073.

11. M.-R. Li, M. Croft, P. W. Stephens, M. Ye, D. Vanderbilt, M. Retuerto, Z. Deng, C. P. Grams, J. Hemberger, J. Hadermann, W.-M. Li, C.-Q. Jin, F. O. Saouma, J. I. Jang, H. Akamatsu, V. Gopalan, D. Walker and M. Greenblatt, Adv. Mater., 2015, 27, 2177-2181.

12. M.-R. Li, P. W. Stephens, M. Retuerto, T. Sarkar, C. P. Grams, J. Hemberger, M. C. Croft, D. Walker and M. Greenblatt, J. Am. Chem.Soc., 2014, 136, 8508-8511.

13. M.-R. Li, M. Retuerto, D. Walker, T. Sarkar, P. W. Stephens, S. Mukherjee, T. S. Dasgupta, J. P. Hodges, M. Croft, C. P. Grams, J. Hemberger, J. Sánchez-Benítez, A. Huq, F. O. Saouma, J. I. Jang and M. Greenblatt, Angew. Chem. Int. Ed., 2014, 53, 10774-10778.

14. M.-R. Li, D. Walker, M. Retuerto, T. Sarkar, J. Hadermann, P. W. Stephens, M. Croft, A. Ignatov, C. P. Grams, J. Hemberger, I. Nowik, P. S. Halasyamani, T. T. Tran, S. Mukherjee, T. S. Dasgupta and M. Greenblatt, Angew. Chem. Int. Ed., 2013, 52, 8406-8410.

15. T.-Y. Yang, W. Wen, G.-Z. Yin, X.-L. Li, M. Gao, Y.-L. Gu, L. Li, Y. Liu, H. Lin, X.-M. Zhang, B. Zhao, T.-K. Liu, Y.-G. Yang, Z. Li, X.-T. Zhou and X.-Y. Gao, Nucl. Sci. Tech., 2015, 26, 020101.

16. M. Gao, Y. L. Gu, L. Li, Z. L. Gong, X. Y. Gao and W. Wen, J. Appl. Crystallogr., 2016, 49, 1182-1189.

17. A. Coelho, J. Appl. Crystallogr., 2000, 33, 899-908.18. Rigaku, 1.3.5 ed., Rigaku Corp., Tokyo, 200219. G. Sheldrick, Acta Crystallogr., Sect. A: Found. Adv. 2015, 71, 3-8. 20. T. K. Mandal, M. Croft, J. Hadermann, G. Van Tendeloo, P. W. Stephens and M. Greenblatt, J.

Mater. Chem., 2009, 19, 4382-4390.21. M. Croft, D. Sills, M. Greenblatt, C. Lee, S. W. Cheong, K. V. Ramanujachary and D. Tran, Phys.

Rev. B (Condensed Matter), 1997, 55, 8726-8732.22. G. Popov, M. Greenblatt and M. Croft, Phys. Rev. B, 2003, 67, 024406.23. Q. S. Lin, M. Greenblatt and M. Croft, J. Solid State Chem., 2005, 178, 1356-1366.24. M. R. Li, M. Retuerto, Z. Deng, P. W. Stephens, M. Croft, Q. Z. Huang, H. Wu, X. Y. Deng, G.

Kotliar, J. Sanchez-Benitez, J. Hadermann, D. Walker and M. Greenblatt, Angew. Chem. Int. Ed., 2015, 54, 12069-12073.

25. D. M. Giaquinta and H.-C. zur Loye, Chem. Mater., 1994, 6, 365-372.26. A. Navrotsky, Chem. Mater., 1998, 10, 2787-2793.27. S. Vasala and M. Karppinen, Prog. Solid State Ch., 2015, 43, 1-36.28. A. Hossain, P. Bandyopadhyay and S. Roy, J. Alloys Compd., 2018, 740, 414-427.29. A. B. Alexei and Y. Wei, J. Phy.: Condens. Matter, 2014, 26, 163201.30. E. Solana-Madruga, A. J. Dos santos-Garcia, A. M. Arevalo-Lopez, D. Avila-Brande, C. Ritter, J. P.

Attfield and R. Saez-Puche, Dalton Trans., 2015, 44, 20441-20448.31. G. V. Bazuev, A. P. Tyutyunnik, M. V. Kuznetsov and Y. G. Zainulin, J. Supercond. Nov. Magn.,

2018, 31, 2907-2914.

12

32. A. J. Dos santos-Garcia, E. Solana-Madruga, C. Ritter, D. Avila-Brande, O. Fabelo and R. Saez-Puche, Dalton Trans., 2015, 44, 10665-10672.

33. A. M. Arevalo-Lopez, F. Stegemann and J. P. Attfield, Chem. Commun., 2016, 52, 5558-5560.34. A. J. D. Santos-García, C. Ritter, E. Solana-Madruga and R. Sáez-Puche, J. Phy.: Condens. Matter,

2013, 25, 206004.35. R. Mathieu, S. A. Ivanov, I. V. Solovyev, G. V. Bazuev, P. Anil Kumar, P. Lazor and P. Nordblad,

Phys. Rev. B, 2013, 87, 014408.36. A. P. Tyutyunnik, G. V. Bazuev, M. V. Kuznetsov and Y. G. Zainulin, Mater. Res. Bull., 2011, 46,

1247-1251.37. A. M. Arévalo-López, G. M. McNally and J. P. Attfield, Angew. Chem. Int. Ed., 2015, 54, 12074-

12077.38. M.-R. Li, P. W. Stephens, M. Croft, Z. Deng, W. Li, C. Jin, M. Retuerto, J. P. Hodges, C. E. Frank,

M. Wu, D. Walker and M. Greenblatt, Chem. Mater., 2018, 30, 4508-4514.39. G.-H. Cai, M. Greenblatt and M.-R. Li, Chem. Mater., 2017, 29, 5447-5457.40. P. M. Woodward, A. W. Sleight, L.-S. Du and C. P. Grey, J. Solid State Chem., 1999, 147, 99-116.41. J. Choisnet, A. Rulmont and P. Tarte, J.Solid State Chem., 1988, 75, 124-135.42. M.-R. Li, E. E. McCabe, P. W. Stephens, M. Croft, L. Collins, S. V. Kalinin, Z. Deng, M. Retuerto,

A. Sen Gupta, H. Padmanabhan, V. Gopalan, C. P. Grams, J. Hemberger, F. Orlandi, P. Manuel, W.-M. Li, C.-Q. Jin, D. Walker and M. Greenblatt, Nat. Commun., 2017, 8, 2037.

43. A. J. Dos santos-García, E. Solana-Madruga, C. Ritter, A. Andrada-Chacón, J. Sánchez-Benítez, F. J. Mompean, M. Garcia-Hernandez, R. Sáez-Puche and R. Schmidt, Angew. Chem. Int. Ed., 2017, 56, 4438-4442.

44. Z.-J. Zhang, T.-T. Jin, M.-M. Xu, Q.-Z. Huang, M.-R. Li and J.-T. Zhao, Inorg. Chem., 2015, 54, 969-975.

45. Á. M. Arévalo-López, E. Solana-Madruga, E. P. Arévalo-López, D. Khalyavin, M. Kepa, A. J. Dos santos-García, R. Sáez-Puche and J. P. Attfield, Phys. Rev. B, 2018, 98, 214403.

46. Y. S. Oh, S. Artyukhin, J. J. Yang, V. Zapf, J. W. Kim, D. Vanderbilt and S.-W. Cheong, Nat. Commun., 2014, 5.

47. S. A. Ivanov, R. Mathieu, P. Nordblad, R. Tellgren, C. Ritter, E. Politova, G. Kaleva, A. Mosunov, S. Stefanovich and M. Weil, Chem. Mater., 2013, 25, 935-945.

48. P. S. Wang, W. Ren, L. Bellaiche and H. J. Xiang, Phys. Rev. Lett., 2015, 114, 147204.49. M.-H. Zhao, W. Wang, Y. Han, X. Xu, Z. Sheng, Y. Wang, M. Wu, C. P. Grams, J. Hemberger, D.

Walker, M. Greenblatt and M.-R. Li, Inorg. Chem., 2019, 58, 1599-1606.50. J. Choisnet, A. Rulmont and P. Tarte, J. Solid State Chem., 1989, 82, 272-278.51. H. Schulz and G. Bayer, Acta Crystallogr. Sec. B, 1971, 27, 815-821.52. G. Blasse and W. Hordijk, J. Solid State Chem., 1972, 5, 395-397.53. R. E. Newnham, J. F. Dorrian and E. P. Meagher, Mater. Res. Bull., 1970, 5, 199-202.54. H. Schulz and G. Bayer, Naturwissenschaften, 1970, 57, 393-393.55. H. Kasper, Z. Anorg. Allg. Chem., 1968, 356, 329-336.56. L. Zhao, Z. Hu, C.-Y. Kuo, T.-W. Pi, M.-K. Wu, L. H. Tjeng and A. C. Komarek, Phys. Status Solidi

RRL, 2015, 9, 730-734.57. S. Ivanov, P. Nordblad, R. Mathieu, R. Tellgren, E. Politova and G. André, Eur. J. Inorg. Chem.,

2011, 2011, 4691-4699.

13

58. N. D. Todorov, M. V. Abrashev, S. C. Russev, V. Marinova, R. P. Nikolova and B. L. Shivachev, Phys. Rev. B, 2012, 85, 214301.

59. G. V. Bazuev, B. G. Golovkin, V. G. Zubkov and A. S. Tyutyunnik, J. Solid State Chem., 1994, 113, 132-137.

60. R. Becker and H. Berger, Acta Crystallogr. Sec. E, 2006, 62, i261-i262.61. B. Wedel, I. Kimio and K. Sugiyama, Z. Kristallogr. NCS, 2001, 216, 345.62. L. Falck, O. Lindqvist and J. Moret, Acta Crystallogr. Sec. B, 1978, 34, 896-897.63. M. Herak, H. Berger, M. Prester, M. Miljak, I. Živković, O. Milat, D. Drobac, S. Popović and O.

Zaharko, J.Phy.: Condens. Matter, 2005, 17, 7667.64. K. Y. Choi, P. Lemmens, E. S. Choi and H. Berger, J. Phy.: Condens. Matter, 2008, 20, 505214.65. H. M, Solid State Commun., 2011, 151, 1588-1592.66. G. Kaleva, E. Politova, S. Ivanov, A. Mosunov, S. Stefanovich, N. Sadovskaya, R. Mathieu and P.

Nordblad, Inorg. Mater., 2011, 47, 1132-1140.67. M. Månsson, K. Prša, J. Sugiyama, D. Andreica, H. Luetkens and H. Berger, Phys. Procedia, 2012,

30, 142-145.68. Z. He and M. Itoh, J. Magn. Magn. Mater., 2014, 354, 146-150.69. X. Zhu, Z. Wang, X. Su and P. M. Vilarinho, ACS Appl. Mater. Inter., 2014, 6, 11326-11332.70. G. Caimi, L. Degiorgi, H. Berger and L. Forró, Europhys. Lett., 2006, 75, 496.71. C. de la Calle, M. J. Martínez-Lope, V. Pomjakushin, F. Porcher and J. A. Alonso, Solid State

Commun., 2012, 152, 95-99.72. M. Weil, Z. Anorg. Allg. Chem., 2003, 629, 653-657.73. R. Becker, M. Johnsson and H. Berger, Acta Crystallogr. Sec. C, 2006, 62, i67-i69.74. H. Singh, A. K. Sinha, H. Ghosh, M. N. Singh and A. Upadhyay, AIP Conf. Proc., 2015, 1665,

060021.75. H. Singh, H. Ghosh, T. V. Chandrasekhar Rao, G. Sharma, J. Saha and S. Patnaik, J. Appl. Phys.,

2016, 119, 044104.76. H. Singh, H. Ghosh, T. V. Chandrasekhar Rao, A. K. Sinha and P. Rajput, J. Appl. Phys., 2014, 116,

214106-214101-214106-214107.77. A. B. Harris, Phys. Rev. B, 2012, 85, 100403.78. J. L. Her, C. C. Chou, Y. H. Matsuda, K. Kindo, H. Berger, K. F. Tseng, C. W. Wang, W. H. Li and

H. D. Yang, Phys. Rev. B, 2011, 84, 235123.79. W.-H. Li, C.-W. Wang, D. Hsu, C.-H. Lee, C.-M. Wu, C.-C. Chou, H.-D. Yang, Y. Zhao, S. Chang,

J. W. Lynn and H. Berger, Phys. Rev. B, 2012, 85, 094431.80. P. Tolédano, V. Carolus, M. Hudl, T. Lottermoser, D. D. Khalyavin, S. A. Ivanov and M. Fiebig,

Phys. Rev. B, 2012, 85, 214439.81. C.-W. Wang, C.-H. Lee, C.-Y. Li, C.-M. Wu, W.-H. Li, C.-C. Chou, H.-D. Yang, J. W. Lynn, Q.

Huang, A. B. Harris and H. Berger, Phys. Rev. B, 2013, 88, 184427.82. M. Weil, Acta Crystallogr. Sec. E, 2006, 62, i246-i247.