Magnetization dynamics: A study of the ferromagnet/antiferromagnet interface and exchange biasing

Abstract

We use a method which employs a dynamic calculation of magnetization motion to find both the static configuration and the spin wave excitations in a ferromagnet/antiferromagnet layered structure. Our results for the static structure are similar to those found in Koon’s model; i.e., in zero applied field the ferromagnet points perpendicularly to the easy axis of the antiferromagnet, and the surface spins of the antiferromagnet are in a surface spin flop configuration. The calculated hysteresis curve for this structure shows a small exchange bias, in agreement with typical experimental results. We explore how this bias depends on the parameters of the antiferromagnet and on the nature of the interface coupling. We further examine models for antiferromagnets with both compensated and uncompensated surfaces. We show that the structure calculated by Koon is unstable at higher reversed magnetic fields but that this instability can be suppressed by an easy-plane anisotropy.