TEM studies of the switching characteristics of small permalloy elements as a function of field orientation

We have studied how the switching field of permalloy elements with sub-micron widths varies as a function of the orientation of the applied field. Switching fields for individual elements were determined using Lorentz microscopy, the studies being facilitated greatly by the use of a newly designed magnetizing stage. Brief details of the stage are given. For elements with widths ∼400 nm, switching fields increased modestly as the angle the applied field made with the long axis of the element increased. In contrast, as the element width was reduced to 160 nm, little variation with field orientation was observed. The results suggest that the residual domain structures close to the ends of the elements played a major role in determining their switching characteristics, even for the smallest elements investigated here