Role of interfacial structure on exchange-biased FeF2-Fe

We have studied the effect of the interface structure on the exchange bias in the FeF2-Fe system, for FeF2 bulk single crystals or thin films. The exc hange bias depends very strongly on the crystalline orientation of the anti ferromagnet for both films and crystals. However, the interface roughness s eems to have a strong effect mainly on the him systems. These results indic ate that the exchange bias depends strongly on the spin structure at the in terface, especially on the angle between the ferromagnetic and antiferromag netic spins. We have also found a strong dependence of the hysteresis loops shape on the cooling field direction with respect to the antiferromagnetic anisotropy axis, induced by a rotation of the ferromagnetic easy axis as t he sample is cooled through T-N. For the single crystal systems the results imply the existence of a perpendicular coupling between the antiferromagne tic and ferromagnetic spins at low temperatures. [S0163-1829(99)02610-7].