Vortex chirality in exchange-biased elliptical magnetic rings

The flux-closed or "vortex" state in thin-film magnetic rings has been proposed as a data storage token, but it has proven difficult to control the vortex chirality in a simple manner. Here, a model is described that predicts the vortex chirality of an elliptical magnetic ring as a function of the direction of the applied field and of the exchange bias, based on the change in energy of the system as the domain walls move. Experimental measurements of chirality in Co and Co/IrMn magnetic rings with 3.2 microm major axis are in excellent agreement with the model. The vortex circulation direction can therefore be tailored with an appropriate combination of applied field direction and exchange bias direction with respect to the major axis.