Anomalous magnetic moment direction under magnetic anisotropy originated from crystalline electric field in van der waals compounds CeTe₃ and CeTe₂Se

The van der Waals compound CeTe₂Se shows that the magnetic moments in the ordered state point along the magnetic hard axis, whereas they point along the magnetic easy axis in CeTe₃. In order to investigate the magnetic properties of CeTe₃ and CeTe₂Se, we performed inelastic neutron scattering experiments, and the crystalline electric field (CEF) excitations were observed. From the CEF analysis, we determined the CEF parameters and revealed that the CEF ground states of CeTe₃ and CeTe₂Se are the same Γ₇⁽¹⁾ and consistent with easy-plane-type magnetic anisotropy. A comparison with other compounds in which the magnetic moments point along the magnetic hard axis suggests that the competition between the CEF ground state and the restriction of magnetic fluctuations by antisymmetric spin-orbit interaction plays an important role in the orientation of the magnetic moment. (author)