A model to predict the upper cap-switch field of various capping layers

In bubble films with a layer of in-plane magnetization, the winding number of the bubbles is changed abruptly as the in-plane field is increased. Measurements of the critical field, the upper cap-switch field, were made on LPE garnet bubble films with capping layers formed of permalloy, YIG grown by CVD, YSmIG grown by LPE, uniaxial garnet grown by LPE, and by ion-implantatlon of the bubble films. To explain the upper cap-switch field, a model is proposed. In the model, the upper cap-switch process is triggered by the structural changes of the planar domains in the capping layer. The critical field of the structural changes is calculated by taking into account the effect of the demagnetizing field arising from the planar domain structure. The agreement between the calculated and measured upper cap-switch field is quite good for all of these capping layers.