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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 Y2CoIrO6 and Y2CoRuO6 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 Y2CoIrO6 and Y2CoRuO6. [ABSTRACT FROM AUTHOR]

Keywords: double perovskites; lattice compression; magnetic frustration; pressure-induced B-site disorder; statistical model EN double perovskites lattice compression magnetic frustration pressure-induced B-site disorder statistical model 8378 8378 1 05/13/20 20200518 NES 200518 B Gemäß chemischer Intuition b erhöht Druck den Ordnungsgrad in den meisten Materialien. Die Entdeckung eines druckinduzierten Unordnungsprozesses in den Doppelperowskiten Y SB 2 sb CoIrO SB 6 sb und Y SB 2 sb CoRuO SB 6 sb steht im Gegensatz zu den klassischen Ordnungs/Unordnungs-Theorien und wird zu einer Neubetrachtung der Druckeffekte in den Festkörperwissenschaften führen. Double perovskites, lattice compression, magnetic frustration, pressure-induced B-site disorder, statistical model. [Extracted from the article]