ANTIFERROMAGNETIC COUPLING BETWEEN CO/NI MULTILAYERS WITH PERPENDICULAR MAGNETIZATION ACROSS MBE-GROWN CU(111) LAYERS

A clear oscillatory exchange coupling has been observed for an epitaxial (111) M1/Cu/M2 structure, grown by Molecular Beam Epitaxy (MBE) on a single crystal Cu(111) substrate. The magnetic layers M1 and M2 were designed to have perpendicular easy axis by using Co/Ni multilayers. The Cu layer was deposited in the form of a wedge. The magneto-optically measured hysteresis loops show, in the case of antiferromagnetic (AF) coupling, clear first-order spin-flip transitions between the saturated and antiparallel states. Signatures of a ferromagnetic or biquadratic component, observed earlier in loops of an AF coupled Co/Cu/Co(111) sandwich, were absent in the present loops. The absence of these signatures is believed to be a consequence of the relatively strong (perpendicular) uniaxial anisotropy of the present samples.