An enhancement behavior of coercivity near TC in ferromagnetic films with uniaxial magnetic anisotropy

Abstract

The temperature dependence of coercivity was investigated in CrO2 and La0.7Sr0.3MnO3 films with and without uniaxial magnetic anisotropy. When the magnetic field was applied along the uniaxial magnetic anisotropy axis, the coercivities of the CrO2 and La0.7Sr0.3MnO3 films showed remarkable enhancement behaviors near ferromagnetic transition temperature (TC). In contrast, CrO2 and La0.7Sr0.3MnO3 films without uniaxial magnetic anisotropy did not exhibit such an enhancement behavior. The temperature dependence of coercivity HC(T) for an aligned Stoner-Wohlfarth ferromagnet was theoretically studied based on a modified model of previously reported ones by He [Phys. Rev. B 75, 184424 (2007)] and Grimsditch [Phys. Rev. Lett. 90, 257201 (2003)]. Experimentally observed enhancement of coercivity near TC could be explained by an effect of a distribution of the local ordering temperatures ρ(TB) for magnetic grains. The qualitative behavior of HC(T) was investigated for three different types of uniaxial anisotropies: (i) magnetocrystalline anisotropy, (ii) strain-induced anisotropy, and (iii) shape anisotropy.