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

Abstract

By performing resonant inelastic x-ray scattering (RIXS) measurements at the Ir ${\mathit{L}}_{3}$ edge, we have investigated the low-energy elementary excitations in a series of double-perovskite iridate single crystals, ${\mathrm{La}}_{2}\mathit{M}{\mathrm{IrO}}_{6} (\mathit{M}=\mathrm{Co},\mathrm{Ni},\phantom{\rule{0.28em}{0ex}}\text{and}\phantom{\rule{0.28em}{0ex}}\mathrm{Zn})$. Almost dispersionless magnetic excitations at $\ensuremath{\sim}42(6)$ meV and $\ensuremath{\sim}35$(5) meV have been observed in crystals containing magnetic $3\mathit{d}$ ions, ${\mathrm{La}}_{2}{\mathrm{CoIrO}}_{6}$ and ${\mathrm{La}}_{2}{\mathrm{NiIrO}}_{6}$, respectively. In contrast, this low-energy magnetic excitation is absent in ${\mathrm{La}}_{2}{\mathrm{ZnIrO}}_{6}$ in which the $3\mathit{d}$ ions are nonmagnetic, suggesting the importance of $3\mathit{d}\ensuremath{-}5\mathit{d}$ 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.