Magnetic excitations in the double-perovskite iridates La2MIrO6 (M=Co,Ni,andZn

Abstract

By performing resonant inelastic x-ray scattering (RIXS) measurements at the Ir L3 edge, we have investigated the low-energy elementary excitations in a series of double perovskite iridate single crystals, La2M IrO6 (M = Co, Ni, and Zn). Almost dispersionless magnetic excitations at ∼ 42(6) meV and ∼ 35(5) meV have been observed in crystals containing magnetic 3d ions, La2CoIrO6 and La2NiIrO6, respectively. In contrast, this low-energy magnetic excitation is absent in La2ZnIrO6 in which the 3d ions are non-magnetic, suggesting the importance of 3d -5d hybridization in the magnetic properties of these double perovskite iridates. The magnetic excitation is suppressed completely above the magnetic ordering temperature, suggesting the inadequacy of using a simple spin Hamiltonian to describe magnetism of these materials.