Lorentz microscopy study of magnetization reversal mechanism in magnetic tunnel junction elements

The magnetization reversal mechanism of four different shaped (rectangular, elliptical, trapezoidal, and hexagonal) tunnel junction elements with area ranging from 0.04 to 12 mum(2) has been investigated using Lorentz transmi ssion electron microscopy. It has been found that the reversal field is inf luenced by element size and aspect ratio but is not strongly dependent upon the element shape. 360 degrees domain walls were often observed to form in the elements and were sustained to a high field when the relative magnetiz ation configuration of the free and pinned layers changed from parallel to antiparallel. The formation of 360 degrees domain walls depends strongly on the shape and aspect ratio of the element, with a lower probability of for mation in elements with either an aspect ratio of 1:1 or a hexagonal shape. (C) 2001 American Institute of Physics.