Magnetic anisotropy in van-der-Waals ferromagnet VI3

TL;DR

This study investigates the magnetocrystalline anisotropy of the layered van-der-Waals ferromagnet VI3, revealing complex angular dependence signals and their relation to structural phases and magnetic regimes.

Contribution

It provides detailed measurements of magnetic anisotropy and its relation to crystal structure in VI3, highlighting the evolution of magnetic signals across different phases and temperatures.

Findings

Magnetization easy axis tilted by ~40° from c axis.

Angular signals change from two-fold to six-fold with temperature.

Structural transitions influence magnetic anisotropy signals.

Abstract

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 "ac" plane perpendicular to and within the basal ab plane, respectively. A two-fold butterfly-like signal was detected by magnetization in the perpendicular "ac" 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 principal c axis by ~40{\deg}. 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 TC. With further cooling, another six-fold-like signal with an angular shift of ~30{\deg} grows approaching TFM. Below TFM, 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 ~30{\deg}.