Angular-dependent magnetic properties in V2O3/Ni hybrid heterostructures

In this paper, we investigate the in-plane angular and temperature dependence of coercivity and exchange bias in a V2O3/Ni magnetic bilayer structure, grown on an r-plane sapphire (alpha-Al2O3) substrate using reactive dc-magnetron sputtering. Distinct variations are observed in coercivity and exchange field across the structural phase transition in V2O3, depending on in-plane angles and different field cooling states, as well as the direction of the applied cooling field. A peak in coercivity, occurring at a temperature corresponding to the phase coexistence region of the V2O3 structural transition, is observed only along the primary easy axis (0 degrees/180 degrees) of the film, disappearing at other angles and remaining independent of the field cooling state. Temperature-dependent measurements, with the applied cooling field along different angles, revealed that the onset of exchange bias at the structural phase transition of the V2O3 occurs irrespective of the cooling field state, yet demonstrates a complex in-plane angular dependence based on the orientation of the applied cooling field. The cooling field orientation influences the exchange bias's anisotropy, magnitude, and direction; notably, a typical unidirectional symmetry emerges when the cooling field aligns with the secondary easy axis (90 degrees/270 degrees) of the film, which nearly aligns with vanadium magnetic moments.