A Pressure‐Induced Inverse Order–Disorder Transition in Double Perovskites
Zheng Deng, Chang‐Jong Kang, Mark Croft, Wenmin Li, Xi Shen, Jianfa Zhao, Richeng Yu, Changqing Jin, Gabriel Kotliar, Sizhan Liu, Trevor A. Tyson, Ryan Tappero, Martha Greenblatt
Abstract
Abstract Given the consensus that pressure improves cation ordering in most of known materials, a discovery of pressure‐induced disordering could require recognition of an order–disorder transition in solid‐state physics/chemistry and geophysics. Double perovskites Y 2 CoIrO 6 and Y 2 CoRuO 6 polymorphs synthesized at 0, 6, and 15 GPa show B‐site ordering, partial ordering, and disordering, respectively, accompanied by lattice compression and crystal structure alteration from monoclinic to orthorhombic symmetry. Correspondingly, the long‐range ferrimagnetic ordering in the B‐site ordered samples are gradually overwhelmed by B‐site disorder. Theoretical calculations suggest that unusual unit‐cell compressions under external pressures unexpectedly stabilize the disordered phases of Y 2 CoIrO 6 and Y 2 CoRuO 6 .