Effect of trigonal distortion induced by strain on the perpendicular magnetic anisotropy of CoV2O4

Abstract

We reported a strain dependence of perpendicular magnetic anisotropy (PMA) in epitaxial CoV2O4 (111) thin films. V3+ sublattice in the CoV2O4 undergoes trigonal distortion, and the t2g level splits into a1g and egπ orbitals. PMA is unveiled below the transition temperature from paramagnetic to collinear ferrimagnetic phase. The spin–orbit coupling (SOC) from V3+egπ orbitals dominates the PMA in the films. The CoV2O4 thin film on the MgAl2O4 substrate suffers a small trigonal distortion and exhibits the largest PMA, with a perpendicular magnetic anisotropy energy (Ku) of 84.2 kJ/m3. Upon cooling, the magnetic order evolves into a non-collinear ferrimagnetic state, accompanied by different moments at the magnetic sites V1 and V2. The V2 spin in the 3D-kagome sublattice is canted. Meanwhile, the PMA is gradually enhanced with decreasing temperature. When the films subjected to larger compressive stress (on Al2O3 or LaAlO3 substrate), the increased energy-level splitting makes the PMA weaken. This work advances the fundamental understanding of orbital-mediated magnetic anisotropy in vanadium-based spinel and demonstrates the feasibility of tailoring magnetic anisotropy via strain-induced structural distortions.