Crystal Structure, Phase Transitions, and Magnetic Properties of Iridium Perovskites Sr2MIrO6 (M = Ni, Zn)

Abstract

Double perovskites containing Ir6+/Ir5+ with formula Sr2MIrO6 (M = Ni, Zn) have been synthesized under high oxygen pressure conditions. Their crystal structures have been studied by X-ray and neutron powder diffraction at room temperature (RT) and 2 K. At RT, these oxides crystallize in the monoclinic space group P21/n with unit-cell parameters a ≈ √2a0, b ≈ √2a0, and c ≈ 2a0, and β ≈ 90°. The thermal evolution of the structure of the Ni-containing compound shows the presence of two phase transition in the 373–673 K interval following the sequence P21/n → I4/m → Fm3̅m. These materials have also been characterized by magnetic measurements, suggesting the onset of antiferromagnetic interactions at TN = 58 and 46 K, for M = Ni, Zn, respectively. X-ray absorption spectroscopy sheds light on the oxidation states of M and Ir ions within these double perovskites.