Local symmetry and magnetic anisotropy in multiferroicMnWO4and antiferromagneticCoWO4studied by soft x-ray absorption …

Soft x-ray absorption experiments on the transition-metal ${L}_{2,3}$ edge of multiferroic ${\text{MnWO}}_{4}$ and antiferromagnetic ${\text{CoWO}}_{4}$ are presented. The observed linear polarization dependence, analyzed by full-multiplet calculations, is used to determine the ground-state wave function of the magnetic ${\text{Mn}}^{2+}$ and ${\text{Co}}^{2+}$ ions. The impact of the local structure and the spin-orbit coupling on the orbital moment is discussed in terms of the single-ion anisotropy. It is shown that the orbital moment in ${\text{CoWO}}_{4}$ is responsible for the collinear antiferromagnetism, while the small size of spin-orbit coupling effects make spiral magnetic order in ${\text{MnWO}}_{4}$ possible, enabling the material to be multiferroic.