Ordered vs. disordered perovskites; structural studies of Fe-doped SrIrO3 and SrRuO3

Abstract

The structures of the two Fe containing perovskites Sr 2 IrFeO 6 and SrRu 0.5 Fe 0.5 O 3 have been established using a combination of synchrotron and neutron diffraction methods. Sr 2 IrFeO 6 and SrRu 0.5 Fe 0.5 O 3 are shown to be monoclinic I2/m and tetragonal I4/mcm respectively The former exhibits a rock-salt like ordering of the Fe and Ir cations and displays a sequence of phase transitions associated with the loss of the octahedral tilts upon heating; 12/m→ I 4/m→ F m 3¯ m. The Fe and Ru cations are disordered in SrRu 0.5 Fe 0.5 O 3 and this shows a single structural phase transition upon heating due to the loss of the in-phase tilts, viz. I 4/m c m→ P m 3¯ m. In both cases XANES measurements show partial oxidation of the Fe 3+ to Fe 4+. The difference in the structures between the two is remarkable given the similar size of Ir 5+ and Ru 5+, and this is reflected in their magnetic properties.