Spin-wave theory of exchange-induced anisotropy

Abstract

It is shown that exchange interactions of spins across the boundary between ferromagnetic and antiferromagnetic layers can cause a shift in the observed hysteresis loop of the ferromagnetic layer. The effect may be interpreted as a self-energy shift of each ferromagnetic spin due to emission and reabsorption of virtual antiferromagnetic spin waves. Emission of these waves by one ferromagnetic spin and reabsorption by another also results in an extra exchange coupling among the ferromagnetic spins, but this is not calculated here in detail. A crucial test of the effectiveness of this mechanism as compared with others that have been proposed would be the observation of a reversal of the loop shift upon reversal of the magnetization of the ferromagnetic layer. However, the reversal time could be very long, and is estimated here. {copyright} {ital 1998} {ital The American Physical Society}