Large Magnetic Anisotropy and Magnetostriction in Thin Films of CoV$_2$O$_4$

TL;DR

This study investigates the magnetic anisotropy and magnetostriction in thin films of CoV$_2$O$_4$, revealing a temperature-induced anisotropy transition and strong low-temperature anisotropy influenced by magnetostriction.

Contribution

It characterizes the structural and magnetic anisotropy transition in CoV$_2$O$_4$ thin films and demonstrates the significant role of magnetostriction in their magnetic behavior.

Findings

Temperature-induced anisotropy change from out-of-plane to biaxial in CoV$_2$O$_4$

Hysteretic features appear below 80 K around hard axes

Magnetostriction significantly influences magnetic anisotropy

Abstract

Spinel Cobalt Vanadate CoV$_2$O$_4$ has been grown on (001) SrTiO$_3$ substrates. Using torque magnetometry experiments, we find that the previously observed temperature induced anisotropy change, where the easy axis changes from the out of plane [001] direction to a biaxial anisotropy with planar <100> easy axes, occurs in a gradual second-order structural phase transition. This work characterizes this transition and the magnetic anisotropies in the (001), (100), and (-110) rotation planes, and explores their field dependence up to 30~T. Below 80~K, hysteretic features appear around the hard axes, i.e., the out-of-plane direction in (-110) and (010) rotations and the planar <110> directions in (001) rotations. This is due to a Zeeman Energy that originates from the lag of the magnetization with respect to the applied magnetic field as the sample is rotated. The appearance of the hysteresis, which persist up to very high fields, shows that the anisotropy at low temperature is rather strong. Additionally, field dependent distortions to the symmetry of the torque response in increasing applied fields shows that magnetostriction plays a large role in determining the direction and magnitude of the anisotropy.