Stress-tailoring magnetic anisotropy of V2O3/Ni bilayers

We report on a temperature-driven reversible change of the in-plane magnetic anisotropy of ${\mathrm{V}}_{2}{\mathrm{O}}_{3}/\mathrm{Ni}$ bilayers. This is caused by the rhombohedral to monoclinic structural phase transition of ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ at ${T}_{C}=160$ K. The in-plane magnetic anisotropy is uniaxial above ${T}_{C}$, but as the bilayer is cooled through the structural phase transition, a secondary magnetic easy axis emerges. Ferromagnetic resonance measurements show that this change in magnetic anisotropy is reversible with temperature. We identify two structural properties of the ${\mathrm{V}}_{2}{\mathrm{O}}_{3}/\mathrm{Ni}$ bilayers affecting the in-plane magnetic anisotropy: (1) a growth-induced uniaxial magnetic anisotropy associated with steplike terraces in the bilayer microstructure and (2) a low-temperature strain-induced biaxial anisotropy associated with the ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ structural phase transition. Magnetoresistance measurements corroborate the change in magnetic anisotropy across the structural transition and suggest that the negative magnetostriction of Ni leads to the emergence of a strain-induced easy axis. This shows that a temperature-dependent structural transition in ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ may be used to tune the magnetic anisotropy in an adjacent ferromagnetic thin film.