Magnetic excitations in the double-perovskite iridates La2MIrO6 (M = Co, Ni, and Zn) mediated by 3d-5d hybridization

초록

By performing resonant inelastic x-ray scattering (RIXS) measurements at the Ir L-3 edge, we have investigated the low-energy elementary excitations in a series of double-perovskite iridate single crystals, La2MIrO6 (M = Co, Ni, and Zn). Almost dispersionless magnetic excitations at similar to 42(6) meV and similar to 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 nonmagnetic, 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.