The influence of end-shape, time and temperature on the switching of small magnetic elements

Summary form only given. In previous a work we have shown that acicular elements with pointed or highly-curved ends switch at considerably higher fields than similarly-sized elements with square ends (Kirk et al. (1997)). Here we report on switching properties of 10nm thick Permalloy elements with widths of 500-700nm and lengths of 2000-3500nm; elements with square or gently-rounded ends were both studied. Specimens were prepared by electron beam lithography and lift-off whilst all observations were made using transmission Lorentz microscopy in a modified Philips CM20 TEM. About 40 notionally identical and well-separated elements of each size and shape were examined. Switching fields at room temperature were typically a few 10´s of Oe, and increased with decreasing element width and were relatively insensitive to element length. Standard deviations of the switching fields within each array were /spl sim/2-30e, attesting to the high quality with which the elements were defined. At elevated temperature (150-250/spl deg/C), switching fields fell markedly to only a few Oe.