Spin-flop tendencies in exchange-biased Co/CoO thin films

In order to study the antiferromagnetic (AFM) spin structure near the inter face of exchange-biased bilayers, polarized neutron diffraction measurement s were performed on a series of (111)Co(7.5 nm)/CoO (X nm) and CoO (X nm) t hin films where X = 20, 40, and 100 nm. In these samples, field cooling thr ough the Neel temperature of the AFM increases the component of the CoO mom ent perpendicular to the applied field, relative to the parallel component. The subsequent application of a 500 Oe field perpendicular to the cooling direction rotates both the Co and CoO moments. Experiments on CoO films wit hout Co showed a smaller difference between the parallel and perpendicular CoO moments in response to cooling and applied fields. Exchange coupling be tween the Co and CoO layers is apparently responsible for the increased pro jection of the AFM moments perpendicular to the cooling field. (C) 1998 Ame rican Institute of Physics.