Effect of frustrations on magnetism in the Ru double perovskiteSr2YRuO6

Abstract

Localized ${\mathrm{Ru}}^{5+}$ spins in ${\mathrm{Sr}}_{2}{\mathrm{YRuO}}_{6}$ form a fcc lattice with an antiferromagnetic (AFM) nearest-neighbor (NN) coupling $J\ensuremath{\approx}25\mathrm{meV}$ and rather low N\'eel temperature ${T}_{N}=26\mathrm{K}.$ Analysis of the electronic structure of ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ results in the effective Heisenberg model. We have studied the effect of frustrations on the AFM type-I structure of ${\mathrm{Sr}}_{2}{\mathrm{YRuO}}_{6}$ in the spin-wave approximation. In the model with only NN coupling the AFM state is unstable due to frustrations, and ${T}_{N}=0.$ Stabilization of the AFM state occurs due to the next-nearest-neighbor coupling I or due to the magnetic anisotropy D. Very small values $D/J\ensuremath{\sim}I/Jl~{10}^{\ensuremath{-}3}$ are enough to obtain the experimental values of ${T}_{N}$ and sublattice magnetization $m=1.85{\ensuremath{\mu}}_{B}/\mathrm{Ru}$ (62% from the nominal $S=3/2$ value).