Magnetic reversal of patterned permalloy thin films

The magnetic domain structure and reversal mechanism in patterned permalloy elements is of great technological importance and is not well understood. The magnetic force microscope (MFM) was used to examine the domain structure in patterned permalloy thin films. The films were patterned into various physical shapes to determine the effects that the edges have on the domain structure and reversal mechanism. The shapes studied were: rectangles, tapered ends with various aspect ratios, triangular notches cut into the bar, triangular notches projecting out from the bar, and holes in the middle of the bar. The uniaxial anisotropy of the permalloy was either parallel to the long axis of the bar or perpendicular. The end shape of the bar had a dramatic influence on the remnant domain structure and the reversal mechanism. The rectangular shape had closure domains and reversed by domain wall motion where the tapered end did not have distinct domains are reversed by a nucleation event. The bars with holes in the middle showed a unique pattern of low angle domain walls near the hole and the hole acted as a nucleation site during magnetic reversal. The bar with triangular notches projecting from it had a large domain extending from the tip of triangle to the opposite side of the bar and reversed by the domain growth of this center domain.