Magnetic anisotropy of the van der Waals ferromagnet Cr_{2}Ge_{2}Te_{6} studied by angular-dependent x-ray magnetic circular dichroism

Abstract

The van der Waals ferromagnet Cr_{2}Ge_{2}Te_{6} (CGT) has a two-dimensional crystal structure where each layer is stacked through van der Waals force. We have investigated the nature of the ferromagnetism and the weak perpendicular magnetic anisotropy (PMA) of CGT by means of x-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD) studies of CGT single crystals. The XMCD spectra at the Cr L_{2,3} edge for different magnetic field directions were analyzed on the basis of the cluster-model multiplet calculation. The Cr valence is confirmed to be 3+ and the orbital magnetic moment is found to be nearly quenched, as expected for the high-spin t_{2g}^{3} configuration of the Cr^{3+} ion. A large (∼0.2 eV) trigonal crystal-field splitting of the t_{2g} level caused by the distortion of the CrTe_{6} octahedron has been revealed, while the single-ion anisotropy (SIA) of the Cr atom is found to have a sign opposite to the observed PMA and too weak compared to the reported anisotropy energy. The present result suggests that anisotropic exchange coupling between the Cr atoms through the ligand Te 5p orbitals having strong spin-orbit coupling has to be invoked to explain the weak PMA of CGT, as in the case of the strong PMA of CrI_{3}.