Magnetic anisotropy in the van der Waals ferromagnet VI3

A comprehensive study of magnetocrystalline anisotropy of a layered van der Waals ferromagnet VI3 was performed. We measured angular dependences of the torque and magnetization with respect to the direction of the applied magnetic field within the basal ab plane and a general orthogonal plane to ab, respectively. A twofold butterflylike signal was detected by magnetization in the orthogonal plane. This signal symmetry remains conserved throughout all magnetic regimes as well as through the known structural transition down to the lowest temperatures. The maximum of the magnetization signal and the resulting magnetization easy axis is significantly tilted from the normal to the basal ab plane by similar to 40 degrees. The close relation of the magnetocrystalline anisotropy to the crystal structure was documented. In contrast, a two-fold-like angular signal was detected in the paramagnetic region within the ab plane in the monoclinic phase, which transforms into a six-fold-like signal below the Curie temperature T-c. With further cooling, another six-fold-like signal with an angular shift of similar to 30 degrees grows approaching T-FM. Below T-FM, in the triclinic phase, the original six-fold-like signal vanishes, being replaced by a secondary six-fold-like signal with an angular shift of similar to 30 degrees