Two types of B-site ordered structures of the double perovskite Y₂CrMnO₆: experimental identification and first-principles study

Abstract

Double perovskite generally exhibits small structure distortion induced by the expansion/contraction and tilting of the BO₆ octahedron. It is difficult to precisely determine their structures, particularly the phase with notable pseudo-symmetry structure and two or more phases with slightly different structures. In this paper, the double perovskite Y₂CrMnO₆ synthesized under high pressure was studied using scanning transmission electron microscopy and first-principles calculations. The new finding is that a rock-salt ordered structure and a layer ordered structure coexist in Y₂CrMnO₆. Similar to the Cu²⁺-based compound, this Mn³⁺-based compound is another new system with layer ordered structure. Unlike the structures of YCrO₃ and YMnO₃, the ordered structure of Y₂CrMnO₆ displays half-metal characteristics.

---

1. Introduction

Single-phase magnetoelectric (ME) material is the most studied multiferroic material, in which ferromagnetic and ferroelectric orders are coexistent.^1–4 ME coupling not only contributes abundant physical mechanisms but also offers numerous potential applications in four-state digital information memory, transducers of ME energy conversion, etc.^5,6 According to the interaction between these two orders, ME materials can be divided into two types of materials:⁷ type-I materials, which exhibit very weak ME couplings and possess different origins for the magnetic and ferroelectric polarization; type-II materials, which possess strong coupling interactions and ferroelectric polarizations, generally related to particular magnetic properties.^8,9

Among the studied type-II ME materials, the perovskite structure materials have received the most attention due to their prominent properties and attractive physical mechanisms.^10–12 It has been known that the properties of perovskites such as the electronic structure, magnetic order and ferroelectric polarization are primarily governed by the B-site ions.^13,14 For instance, YCrO₃ exhibits a monoclinic structure and belongs to the type-I ME material family. It shows weak ferromagnetism below 140 K, stemming from a canted antiferromagnetic order and displays ferroelectricity below 473 K, originating from chromium displacements along the z-direction.^15,16 An opposite instance is orthorhombic YMnO₃, which belongs to the type-II ME material family.^17,18 Neutron diffraction and magnetization measurements on the polycrystalline sample have demonstrated that YMnO₃ has a magnetic order below the Néel temperature of 42 K and ferroelectric order below 31 K.^19,20 The ferroelectricity is caused by shifts of oxygen ions due to the inverse Dzyaloshinskii–Moriya (DM) interaction.^20–23 Further consideration of the exceptional structure and compositional flexibility of the perovskite structure shows that it is possible to tune the properties through substituting the B site ion.¹⁴ Unfortunately, this substitution is accompanied by the expansion/contraction and tilting of the BO₆ octahedron to accommodate the crystal structure.²⁴ The crucial point in detecting the slight octahedral distortion is to determine the oxygen atom position. Therefore, it is difficult to precisely determine the crystal structure with a tiny distortion of the BO₆ octahedron by X-ray diffraction (XRD), neutron diffraction, electron diffraction or synchrotron radiation particularly when heavy elements are present.^25,26 If the phase has either a notable pseudo-symmetry structure or two slightly different structures that are coexistent, the traditional measurement methods become incapable.

In this study, we investigate the crystal Y₂CrMnO₆, which contains B-site ions of Cr³⁺ and Mn³⁺. It should be noted that Mn³⁺ is a Jahn–Teller ion, which can induce octahedral expansion/contraction along a direction, while the Cr³⁺ ion does not exhibit this effect.²⁷ In addition to the differences in ion radius and electronic structure between these two ions, Y₂CrMnO₆ should possess structures and properties different from YMnO₃ and YCrO₃. High angle annular dark field (HAADF) imaging, annular bright field (ABF) imaging, and selected area electron diffraction (SAED) measurements were performed to detect the structure of Y₂CrMnO₆. Peak pair analysis (PPA) software and Cambridge serial total energy package (CASTEP) method were applied to further analyze these structures. Image simulation technology was also used to examine the proposed structures. Finally, the physical properties were investigated by the first-principles calculations.

2. Experimental section

2.1 Synthesis of single crystal powders of Y₂CrMnO₆ ²⁸

The sample was synthesized by two steps. The YCrO₃ (or hexagonal YMnO₃) powder was used as a precursor and prepared through the solid state reaction between Y₂O₃ and Cr₂O₃ (or Mn₂O₃) at 1573 K under ambient pressure. Then, the YCrO₃ and hexagonal YMnO₃ powders were mixed completely and loaded into a platinum capsule with a flux of H₂O and KCl. Subsequently, the powders were heated at 1573 K under 6 GPa for 2 h. Finally, the obtained products were quenched to room temperature and washed with distilled water to remove KCl.

2.2 TEM sample preparation

The specimens for transmission electron microscopy (TEM) were prepared by the traditional powder sample preparation method. The synthesized powders were placed into alcohol solution and ground in an agate mortar for about 20 min and then ultrasonically concussed for 20 min. Finally, the mixture was placed onto a copper grid covered with lacey carbon film.

2.3 TEM observations

The scanning transmission electron microscopy (STEM) (HAADF and ABF) and SAED were performed on a JEM-ARM200F microscope with double Cs correctors for the condenser lens and objective lens. The available point resolution was better than 0.078 nm at an operating voltage of 200 kV. The acceptance angles were 90–370 mrad for HAADF imaging and 10–20 mrad for ABF imaging. All the images shown in this text were Fourier-filtered to minimize the effect of contrast noise. The filtering had no effect on the measurements.

2.4 Theoretical calculations

For Y₂CrMnO₆, the structure optimization and density of states (DOSs) were both calculated by the method of generalized gradient approximation plus U (GGA + U) in CASTEP.

2.5 Characterizations of magnetic properties

The magnetic properties were measured using the superconducting quantum interference device system (SQUID, Quantum Design Inc.).

3. Results and discussion

Fig. 1 shows STEM images of a Y₂CrMnO₆ grain along the [100] direction indexed to the structure of orthorhombic YMnO₃. The YMnO₃ structure, with a space group of Pnma, is shown in Fig. 1(b). Fig. 1(a) displays an HAADF image, in which the bright dot locations correspond to the atomic columns and the intensity is proportional to Z^1.7, where Z is the relative atomic number.^29,30 On the basis of the YMnO₃ structure, the bright dots can be marked out by the relative atom columns as shown in the inset of Fig. 1(a). The corresponding SAED pattern (inset of Fig. 1(a)) shows diffraction spots similar to those of orthorhombic YMnO₃. Moreover, the corresponding ABF image and its colored enlarged portion are displayed in Fig. 1(c) and (d), respectively. According to ABF imaging theory, the dark dot locations represent the atomic columns and the intensity is proportional to Z^1/3.^31,32 The merit of ABF imaging technology is that the contrast of the image is sensitive to the light atoms, such as lithium and oxygen.^33,34 Therefore, it is beneficial to check the structure change induced by these atoms. From Fig. 1(c) and (d), it can be observed that this ABF image presents a fascinating phenomenon, in which the dark points (pointed by the arrows) between the M-site atoms show an alternating arrangement along both the y and z directions. In the orthorhombic YMnO₃ with space group Pnma, these points correspond to the double oxygen atomic columns and have equivalent crystallography positions, while the alternative arrangement occurs in Y₂CrMnO₆. The ordered arrangement in Y₂CrMnO₆ indicates a crystal structure different from that of YMnO₃. Considering the difference in composition between Y₂CrMnO₆ and YMnO₃, it is reasonable to speculate that the order of double oxygen atoms of this type can be induced by M atom ordered structure. Referring to the B-site ion ordered double perovskites, this Y₂CrMnO₆ structure corresponds to rock-salt ordered structure.¹⁴ This is the most common type of B-site ordering in the known double perovskites;^35,36 nevertheless, it has not yet been reported in Y₂CrMnO₆.

Fig. 1 (a) HAADF image of Y₂CrMnO₆ along the [100] direction indexed to the space group of Pnma of YMnO₃, with inset showing corresponding SAED pattern; (b) structure diagram of YMnO₃; (c) ABF image and (d) enlarged part of Y₂CrMnO₆ along the [100] direction.

In order to clearly understand this type of ordered structure, more detailed analyses were performed. The inverse ABF image (IABF) of Fig. 1(c) was chosen for the peak pair analysis (PPA) software³⁷ and the results are shown in Fig. 2(a). A partial image, as shown in Fig. 2(b), was selected for structure analyses and the results are shown in Fig. 2(c–e). The Y–Y distances between adjacent rows are denoted as red circles (Y₁–Y₂) and black squares (Y₂–Y₃), and the data demonstrate that these two distances show no evident difference as shown in Fig. 2(c). The distances between M and the nearest Y ions along the y-direction are also shown in Fig. 2(d). It is clear that the distances of Y_A–M (denoted by the purple stars) are larger than those of M–Y_B (denoted by dark cyan left triangles) and the corresponding average values are 19.01 (±0.25) and 18.34 (±0.30) pixels, respectively (one pixel denotes 9.6 pm). Fig. 2(e) shows the distances between two nearest Y ions along the z-direction. The measurements for five layers along the z direction are presented, and the numbers along the horizontal direction denote the sequence numbers of Y–Y along the y direction. It is easy to observe that the distance between two Y ions varies in a large–small–large–small… manner along the y-direction in each layer; it shows an opposite trend between the nearest layers, i.e., a smallest distance in one layer corresponds to a largest distance in the two nearest layers and vice versa.

Fig. 2 ((a), (b)) IABF images corresponding to Fig. 1(c) and enlarged partial image; ((c)–(e)) distance distributions of the Y₁–Y₂, Y₂–Y₃, Y_A–M, M–Y_B, Y_C–Y_D; according to the experimental condition, one pixel denotes 9.6 pm; (f) rock-salt ordered structure diagram of Y₂CrMnO₆.

Based on the above discussion, we propose a structural model corresponding to the rock-salt ordered structure with a space-group of Pc (No. 7) (see ESI†) and have modified it by the first-principles method. The modified structure diagram is shown in Fig. 2(f).

Fig. 3(a) displays the HAADF image of another Y₂CrMnO₆ grain along the [101] direction indexed to the YMnO₃ structure as shown in Fig. 3(b). The Y and M atoms are interpreted in Fig. 3(a). It can be observed that the bright spots corresponding to the atomic columns and the inserted SAED pattern are consistent with the scenario of orthorhombic YMnO₃ structure. The interesting point is that the corresponding ABF image shown in Fig. 3(c) displays an alternative arrangement of bright and gray belts along the horizontal direction. An enlarged color image is presented in Fig. 3(d). For the space group Pnma, these belts should be equal in width. Therefore, the ordered contrast arrangement signifies that the structure of Y₂CrMnO₆ is different from that of orthorhombic YMnO₃. Further, we exclude it from the rock-salt structure mentioned above through structure analysis and the ABF image simulation.

Fig. 3 (a) HAADF image of Y₂CrMnO₆ along the [101] direction indexed to YMnO₃, with inset showing the corresponding SAED pattern; (b) structure diagram of YMnO₃; (c) ABF image and (d) partial enlarged ABF image of Y₂CrMnO₆ along the [101] direction.

Fig. 4(a) shows the IABF image corresponding to Fig. 3(c). The intensity profile of the M atoms along the horizontal direction, indicated by dotted yellow lines, is shown by the yellow curve in Fig. 4(a). It is clear that the intensity of the corresponding M atomic columns presents an ordered alternative arrangement in a strong-substrong-strong-substrong… manner. Since the M atoms at the B site are replaced by Cr and Mn ions, it is reasonable to assume that these two intensities can respectively correspond to these two different ions. In order to obtain more detailed structural information, the region marked by the red lines in Fig. 4(a) was chosen as a basic analytical unit. The involved Y and M atoms are marked as M₁, M₂, Y₁, Y₂, Y₃, Y₄, Y₅, and Y₆.

Fig. 4 (a) IABF image corresponding to Fig. 3(c) and enlarged part of image; the yellow curve represents the intensity profile of the M atoms; ((b)–(d)) distance distributions of M₁–Y₁, M₁–Y₂, M₁–Y₃, M₁–Y₄, M₂–Y₃, M₂–Y₄, M₂–Y₅, M₂–Y₆, Y_1,2–Y_3,4, Y_3,4–Y_5,6 (according to the experimental condition, one pixel denotes 9.6 pm); (e) layer ordered structure diagram of Y₂CrMnO₆.

To understand the formation of this superstructure, the distances of Y–Y and Y–M were studied. Fig. 4(b) shows the distances between M₁ atom and its four nearest Y atoms. It is evident that the distances M₁–Y₁ (purple down-triangle) and M₁–Y₂ (pink down-triangle) are larger than those of M₁–Y₄ (dark cyan diamond) and M₁–Y₃ (olive diamond). The average distances are 29.75 (±0.56) pixels for M₁–Y₁, 25.94 (±0.83) pixels for M₁–M₂, 24.26 (±0.81) pixels for M₁–Y₃, and 27.96 (±0.91) pixels for M₁–Y₄. The distances between M₂ atom and the four nearest Y atoms were also calculated and the results are shown in Fig. 4(c). Similarly, the distances of M₂–Y₃ (pink star) and M₂–Y₄ (magenta star) are larger than those of M₂–Y₆ (blue up-triangle) and M₂–Y₅ (dark yellow up-triangle). The average values are 25.64 (±0.68) pixels for M₂–Y₃, 29.55 (±0.98) pixels for M₂–Y₄, 28.27 (±0.85) pixels for M₂–Y₅, and 24.57 (±0.76) pixels for M₂–Y₆. The angles between the lines from M₁ and M₂ to their own nearest Y atoms were also detected. Fig. 4(d) shows the variations of the distance between the nearest Y rows along the horizontal direction with distance number. These two sets of distances, namely, Y_1,2–Y_3,4 (blank squares) and Y_3,4–Y_5,6 (red circles), have no significant difference.

Compared with the structure of orthorhombic YMnO₃, the structure of Y₂CrMnO₆ shows that the M atoms at B-sites present an alternating layered arrangement of Cr and Mn ion along the horizontal direction, while Y atom coordinates remain almost unchanged. This structure is generally called the layer ordered structure of double perovskite¹⁴ and has been reported only in the Cu²⁺-based double perovskites.^38–40 In addition, these two kinds of B-site atoms have different displacements along the horizontal direction, namely, 5.89 pm for Mn atoms in gray belts in the ABF image and 3.92 pm for Cr atoms in bright belts. Through careful structural analyses, it can be judged that the Y₂CrMnO₆ structure of this type is space group monoclinic structure Pc (No. 7) instead of orthorhombic structure Pnma (No. 62). Unfortunately, the chaotic distribution of oxygen atoms along this crystal axis, resulting from the distortion and tilting of the MO₆ octahedron, makes it difficult to obtain accurate coordinates of oxygen atoms. Hence, first-principles calculations were carried out to acquire a reasonable crystal structure of Y₂CrMnO₆. The schematic diagram of the crystal structure is presented in Fig. 4(e) and the detailed crystal structure data are provided in the ESI.†

Since these two types of ordered structures were distinguished by ABF images, it is necessary to perform image simulations to verify the determined crystal structure. The STEM-ABF images were simulated with the xHREM software and results are shown in Fig. 5. The applied parameters were based on the experimental parameters. It is evident that the simulated image of the rock-salt ordered structure shows the alternative arrangement of double oxygen atoms (pointed by the arrows, Fig. 5(a)) and the simulated image of the layer ordered structure shows the alternative arrangement of bright and gray belts (Fig. 5(b)). The SAED patterns and HAADF images were also simulated. All the simulated images were in accordance with the experimental images, indicating the correctness of the proposed structures.

Fig. 5 Simulated ABF images and their enlarged parts of (a) the rock-salt ordered and (b) the layer ordered Y₂CrMnO₆; colored images show the details of enlarged parts.

The first-principles calculations were carried out for the different spin configurations for the rock-salt ordered and layer ordered structures of Y₂CrMnO₆, and the results are shown in Table 1. The arrows represent the spin directions of the transition metal ions. It can be seen that, for either rock-salt ordered or layer ordered structure, the ferromagnetic spin configuration (Cr₁↑Cr₂↑Mn₁↑Mn₂↑) exhibits the lowest binding energy and thus is the most stable structure. The ferromagnetic properties of the prepared Y₂CrMnO₆ sample were also checked by zero field cooled (ZFC), field cooled (FC) and field dependence of magnetization (M–H) and the results are shown in Fig. 6. The ZFC, FC and M–H curves of the Y₂CrMnO₆ sample clearly infer the ferromagnetic properties. It should be noted that the binding energies for the two ordered structures are almost equal as listed in Table 1; this is a possible reason for coexistence of these two ordered structures. Fig. 7 shows the spin-polarized densities of states (DOSs) of the two ordered structures of Y₂CrMnO₆. From the total DOSs of the rock salt ordered Y₂CrMnO₆ (Fig. 7(a)), it can be observed that only the up-spin state exists at the Fermi level, indicating its half-metal properties. Referring to the partial DOSs of 3d electrons of Cr and Mn atoms, both elements contribute the up-spin state. Similar results are also obtained for the layer ordered structure. Therefore, both ordered structures possess half-metal characteristics.

Fig. 6 ZFC, FC and M-H curves of Y₂CrMnO₆; the ZFC and FC were measured in a magnetic field of H = 1000 Oe.

Fig. 7 Spin-polarized DOSs of (a) the rock-salt ordered and (b) layer ordered Y₂CrMnO₆.

Table 1 Binding energies of Y₂CrMnO₆ with different spin configurations for rock-salt ordered and layer ordered structures. The arrows represent the spin directions of the transition metal ions

Y2CrMnO6	Binding energy (eV f.u.^−1)
	Rock-salt ordered structure	Layer ordered structure
Cr1↑Cr2↑Mn1↑Mn2↑	−75.373	−75.366
Cr1↑Cr2↑Mn1↓Mn2↓	−75.183	−75.318
Cr1↑Cr2↓Mn1↑Mn2↓	−75.272	−75.064
Cr1↑Cr2↓Mn1↓Mn2↑	−75.289	−75.025
Cr1↑Cr2↓Mn1↓Mn2↓	−75.180	−75.304
Cr1↓Cr2↑Mn1↓Mn2↓	−75.180	−75.205
Cr1↓Cr2↓Mn1↑Mn2↓	−75.173	−74.825
Cr1↓Cr2↓Mn1↓Mn2↑	−75.173	−74.743

---

4. Conclusions

The Y₂CrMnO₆ synthesized by high pressure method exhibited two types of coexistent ordered structures: rock-salt ordered structure and layer ordered structure. These ordered structures were inferred from ABF images. The ABF image along the [100] axis of the rock-salt ordered structure shows an alternative arrangement of double oxygen atoms along the y- and z-directions, while the ABF image along the [101] axis shows an alternating arrangement of bright and gray belts along the y-direction. Combining PPA software with CASTEP, two possible ordered structures were proposed. All the simulated images show good agreement with experimental ones, verifying the correctness of the suggested structures. The first-principles calculations indicated that these two ordered structures of Y₂CrMnO₆ both have half-metal characteristics, which are totally different from those of YCrO₃ and YMnO₃.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was supported by the National key research program of China (Grant No. 2016YFA0300701, 2017YFA0206200) and the National Natural Science Foundation of China (Grant No. 11174336, 11374343).

References

1. W. Eerenstein, N. D. Mathur and J. F. Scott, Nature, 2006, 442, 759–765.
2. M. Fiebig, J. Phys. D: Appl. Phys., 2005, 38, R123–R152.
3. C.-W. Nan, M. I. Bichurin, S. Dong, D. Viehland and G. Srinivasan, J. Appl. Phys., 2008, 103, 031101.
4. C. A. Vaz, J. Hoffman, C. H. Ahn and R. Ramesh, Adv. Mater., 2010, 22, 2900–2918.
5. J. F. Scott, Nat. Mater., 2007, 6, 256–257.
6. J. G. Wan, Z. Y. Li, Y. Wang, M. Zeng, G. H. Wang and J. M. Liu, Appl. Phys. Lett., 2005, 86, 202504.
7. D. I. Khomskii, J. Magn. Magn. Mater., 2006, 306, 1–8.
8. Y. Tokura and S. Seki, Adv. Mater., 2010, 22, 1554–1565.
9. H. Murakawa, Y. Onose, S. Miyahara, N. Furukawa and Y. Tokura, Phys. Rev. Lett., 2010, 105, 137202.
10. L. Yan, Y. Yang, Z. Wang, Z. Xing, J. Li and D. Viehland, J. Mater. Sci., 2009, 44, 5080–5094.
11. S. Dong and J.-M. Liu, Mod. Phys. Lett. B, 2012, 26, 1230004.
12. H. Wu, L. Li, L.-Z. Liang, S. Liang, Y.-Y. Zhu and X.-H. Zhu, J. Eur. Ceram. Soc., 2015, 35, 411–441.
13. A. A. Belik, J. Solid State Chem., 2012, 195, 32–40.
14. S. Vasala and M. Karppinen, Prog. Solid State Chem., 2015, 43, 1–36.
15. K. Ramesha, A. Llobet, T. Proffen, C. R. Serrao and C. N. R. Rao, J. Phys.: Condens. Matter, 2007, 19, 102202.
16. C. R. Serrao, A. K. Kundu, S. B. Krupanidhi, U. V. Waghmare and C. N. R. Rao, Phys. Rev. B: Condens. Matter Mater. Phys., 2005, 72, 2201101.
17. S. X. Lin, X. G. Fang, A. H. Zhang, X. B. Lu, J. W. Gao, X. S. Gao, M. Zeng and J. M. Liu, J. Appl. Phys., 2014, 116, 163705.
18. H. Wadati, J. Okamoto, M. Garganourakis, V. Scagnoli, U. Staub, Y. Yamasaki, H. Nakao, Y. Murakami, M. Mochizuki, M. Nakamura, M. Kawasaki and Y. Tokura, Phys. Rev. Lett., 2012, 108, 047203.
19. B. Lorenz, Y.-Q. Wang and C.-W. Chu, Phys. Rev. B: Condens. Matter Mater. Phys., 2007, 76, 104405.
20. J. Kim, S. Jung, M. S. Park, S.-I. Lee, H. D. Drew, H. Cheong, K. H. Kim and E. J. Choi, Phys. Rev. B: Condens. Matter Mater. Phys., 2006, 74, 052406.
21. I. A. Sergienko and E. Dagotto, Phys. Rev. B: Condens. Matter Mater. Phys., 2006, 73, 094434.
22. D. Okuyama, S. Ishiwata, Y. Takahashi, K. Yamauchi, S. Picozzi, K. Sugimoto, H. Sakai, M. Takata, R. Shimano, Y. Taguchi, T. Arima and Y. Tokura, Phys. Rev. B: Condens. Matter Mater. Phys., 2011, 84, 054440.
23. I. A. Sergienko, C. Sen and E. Dagotto, Phys. Rev. Lett., 2006, 97, 227204.
24. J. Fontcuberta, C. R. Physique, 2015, 16, 204–226.
25. Q. Zhou, T.-Y. Tan, B. J. Kennedy and J. R. Hester, J. Solid State Chem., 2013, 206, 122–128.
26. W. T. Fu, R. J. Götz and D. J. W. Ijdo, J. Solid State Chem., 2010, 183, 419–424.
27. N. D. Todorov, M. V. Abrashev, V. G. Ivanov, G. G. Tsutsumanova, V. Marinova, Y. Q. Wang and M. N. Iliev, Phys. Rev. B: Condens. Matter Mater. Phys., 2011, 83, 224303.
28. F. Liu, J. Li, Q. Li, Y. Wang, X. Zhao, Y. Hua, C. Wang and X. Liu, Dalton Trans., 2014, 43, 1691–1698.
29. H. R. P. Hartel and C. Dinges, Ultramicroscopy, 1996, 63, 93–114.
30. R. F. Loane, E. J. Kirkland and J. Silcox, Acta Crystallogr., Sect. A: Found. Crystallogr., 1988, 44, 912–927.
31. S. D. Findlay, N. Shibata, H. Sawada, E. Okunishi, Y. Kondo and Y. Ikuhara, Ultramicroscopy, 2010, 110, 903–923.
32. S. D. Findlay, N. Shibata, H. Sawada, E. Okunishi, Y. Kondo, T. Yamamoto and Y. Ikuhara, Appl. Phys. Lett., 2009, 95, 191913.
33. X. He, L. Gu, C. Zhu, Y. Yu, C. Li, Y.-S. Hu, H. Li, S. Tsukimoto, J. Maier, Y. Ikuhara and X. Duan, Mater. Express, 2011, 1, 43–50.
34. H. Hojo, T. Mizoguchi, H. Ohta, S. D. Findlay, N. Shibata, T. Yamamoto and Y. Ikuhara, Nano Lett., 2010, 10, 4668–4672.
35. P. K. Dager, C. M. Chanquía, L. Mogni and A. Caneiro, Mater. Lett., 2015, 141, 248–251.
36. T. K. Wallace, C. Ritter and A. C. McLaughlin, J. Solid State Chem., 2012, 196, 379–383.
37. P. L. Galindo, S. Kret, A. M. Sanchez, J.-Y. Laval, A. Yáñez, J. Pizarro, E. Guerrero, T. Ben and S. I. Molina, Ultramicroscopy, 2007, 107, 1186–1193.
38. Q. Zhou and B. J. Kennedy, J. Phys. Chem. Solids, 2007, 68, 1643–1647.
39. S. Vasala, H. Saadaoui, E. Morenzoni, O. Chmaissem, T.-S. Chan, J.-M. Chen, Y.-Y. Hsu, H. Yamauchi and M. Karppinen, Phys. Rev. B: Condens. Matter Mater. Phys., 2014, 89, 134419.
40. M. Gateshki, J. M. Igartua and E. Hernandez-bocanegra, J. Phys.: Condens. Matter, 2003, 15, 6199–6217.

---

Footnote

† Electronic supplementary information (ESI) available: The detailed crystal structure data of the rock-salt ordered Y₂CrMnO₆ and layer ordered Y₂CrMnO₆. See DOI: 10.1039/c7qi00686a

---