Anisotropic magnetoresistance of La_(0.7)Ca_(0.3)MnO_3 thin film biepitaxial step junctions

摘要

The angular dependence of magnetoresistance (MR) of the La_(0.7)Ca_(0.3)MnO_3 thin film biepitaxial step junction (BSJ) shows a simple sin~2(θ) dependence in the in-plane high-field magnetoresistance, with θ being the angle between the applied field and current. This behavior is similar to the spin-orbit coupling-induced anisotropic magnetoresistance (AMR) commonly observed in transition ferromagnetic metals, except for two salient features. First, the maximum MR in the present case occurs at an oblique angle between the applied field (H) and electric current (I), while it is usually observed to occur when H‖I. Second, the AMR in the plane perpendicular to the film surface displays a remarkable value (Δρ/ρ～ 8 %), which is about an order of magnitude larger than that of the in-plane AMR. Such a large AMR cannot be solely explained by spin-orbit coupling effect. We suggest instead that the metallic and ferromagnetic inhomogeneous granules existing in the BSJ region might have acted as the source of spin-polarized scattering giving rise to the enhanced AMR when the colossal magnetoresistance was measured across the biepitaxial step boundaries.