Spin-Polarized Transport across Sharp Antiferromagnetic Boundaries

We report spin-polarized transport experiments across antiphase domain boundaries which act as atomically sharp magnetic interfaces. The antiphase boundaries are prepared by growing ${\mathrm{Fe}}_3{\mathrm{O}}_4$ epitaxially on MgO, the magnetic coupling over a large fraction of these boundaries being antiferromagnetic. Magnetoresistance measurements yield linear and quadratic field dependence up to the anisotropy field for fields applied parallel and perpendicular to the film plane, respectively. This behavior can be explained by a hopping model in which spin-polarized electrons traverse an antiferromagnetic interface between two ferromagnetic chains.