Fourfold symmetric anisotropic magnetoresistance based on magnetocrystalline anisotropy and antiphase boundaries in reactive sputtered epitaxial Fe3O4 films

The fourfold symmetric anisotropic magnetoresistance (AMR) at high fields in epitaxial Fe3O4 films, which is incompatible with the traditional twofold symmetry, was found to be independent with the current direction but associated with their magnetocrystalline anisotropy. (001)-, (110)-, and (112)-oriented Fe3O4 films show fourfold symmetry in AMR while twofold symmetry appears for (111)-oriented Fe3O4 films. The cubic magnetocrystalline anisotropy field superimposed onto the external magnetic field modifies the alignment of the spins near antiphase boundaries, leading to the oscillating scattering rate for the transport electrons across antiphase boundaries and thus the corresponding fourfold symmetry in AMR.