Spin-dependent six-fold symmetric anisotropic magnetoresistance in epitaxial magnetite films

Six-fold anisotropic magnetoresistance (AMR) was observed in epitaxial Fe3O4(1 1 1) films on conductive ZnO (0 0 0 1), while the current flowed perpendicularly to the film plane and the magnetic field rotated in the film plane, demonstrating the close relation between AMR and magnetocrystalline anisotropy. The spin injection efficiency of Fe3O4 films was modulated from 60% to 20% with increasing underlayer ZnO surface roughness through changing the sputtering pressure. Larger AMR is observed in epitaxial Fe3O4(1 1 1) films with higher spin injection efficiency. Under the induction of a magnetic field and magnetocrystalline anisotropic fields along the easy axis, it is supposed that the scattering of carriers by the noncollinear moments near antiphase boundaries is weaker for the films with higher spin injection efficiency.