Crystal Structures and Properties of Perovskites ScCrO₃ and InCrO₃ with Small Ions at the A Site

ScCrO3 and InCrO3 were synthesized at high pressure of 6 GPa and 1500 K. Crystal structures of ScCrO3 and InCrO3 were studied with synchrotron X-ray powder diffraction. They crystallize in the GdFeO3-type perovskite structure (space group Pnma, a = 5.35845(1) Å, b = 7.37523(1) Å, c = 5.03139(1) Å for ScCrO3 and a = 5.35536(1) Å, b = 7.54439(1) Å, c = 5.16951(1) Å for InCrO3). The physical properties of ScCrO3 and InCrO3 were investigated with specific heat, ac/dc magnetization, and dielectric measurements and compared with those of YCrO3 with nonmagnetic Y3+ ions at the A site. Antiferromagnetic transitions occur at TN = 73 K in ScCrO3 and 93 K in InCrO3 in agreement with the general trend of ACrO3 (A = Y and rare earths) where TN decreases with decreasing the radius of the A ions. Extremely weak ferromagnetism was found in ScCrO3 and InCrO3 in contrast to YCrO3. Ac magnetization measurements revealed some peculiarities in behavior of ScCrO3 and InCrO3, namely, double-peak anomalies just below TN. Dielectric anomalies were observed in both compounds at TN indicating magnetoelectric coupling in contact with YCrO3 where no dielectric anomalies were found. ScCrO3 and InCrO3 are very stable for high-pressure phases: no decomposition of ScCrO3 was observed after heating up to 1340 K in air, and InCrO3 only partially decomposed at 1340 K to give Cr2O3 and ambient- and high-pressure modifications of In2O3 as impurities. No anomalies were also found with differential scanning calorimetry up to 870 K and differential thermal analysis up to 1340 K, indicating the absence of high-temperature phase transitions.