Origin of the anomalous magnetic behaviour in single crystal Fe3O4 films

Antiphase boundaries (APBs) were observed in Fe3O4 single crystal films grown on MgO. The APBs are an intrinsic consequence of the nucleation and growth mechanism in films. Across an APE, the intrasublattice superexchange coupling is greatly strengthened, while the intersublattice superexchange coupling Is weakened, reversing the dominant interaction from that found in the bulk. Thus the APE separates oppositely magnetized regions. consistent with Lorentz microscopy measurements. The APBs Induce very large saturation fields and nearly random magnetization distribution in zero field.