Antiferromagnetic Coupling in Sputtered MgO Tunnel Junctions With Perpendicular Magnetic Anisotropy

Antiferromagnetic coupling between magnetic electrodes has been observed in non-epitaxial perpendicularly magnetized MgO tunnel junctions. This coupling becomes less negative with increasing annealing temperature up to 375 degrees C. This can be possibly related to homogeneization of oxygen in the barrier and de-oxidation of the magnetic electrodes. However, the evolution of coupling field with both barrier and electrode thickness doesn't agree with existing coupling theories. Similar structures with in-plane magnetized electrodes exhibit classical ferromagnetic coupling.