LONG-RANGE EXCHANGE COUPLING BETWEEN A FERROMAGNET AND AN ANTIFERROMAGNET ACROSS A NONMAGNETIC SPACER LAYER

The antiferromagnet/ferromagnet exchange coupling giving rise to a shi fted hysteresis loop has usually been considered an interfacial effect . We show evidence that this exchange coupling between an antiferromag net (CoO) and a ferromagnet (Ni81Fe19) is long range in nature. Exchan ge coupling has been observed in tri-layer films consisting of a nonma gnetic noble metal (Ag, Au, and Cu) spacer layer sandwiched between 30 0 Angstrom CoO and 300 Angstrom NiFe. The strength of the coupling dec reases with increasing spacer layer thickness and vanishes at about 55 Angstrom. This suggests that the antiferromagnetic/ferromagnetic exch ange coupling is beyond an interfacial effect, and that conduction ele ctrons may be involved in the mediation of the coupling. (C) 1997 Amer ican Institute of Physics.