Micromagnetism and magnetization reversal of micron-scale (110) Fe thin-film magnetic elements

Abstract

Magnetic force microscope (MFM) imaging in conjunction with longitudinal Kerr hysteresis loop measurements have been used to investigate the micromagnetic behavior of micron scale epitaxial (110) bcc Fe thin-film elements (50-nm thick) with rectangular, triangular, and needle-shaped ends and competing magnetic anisotropies. Thin-film elements of 2-mm width and 6-mm length and greater have been fabricated with their long axis oriented either parallel or perpendicular to the [001] in-plane magnetocrystalline easy axis. For elements with their long axis perpendicular to the [001] direction, the end shape is critical in determining domain nucleation, domain configurations, and magnetic hysteresis. The magnetization reversal mechanisms are revealed by direct field dependent MFM imaging. Magnetic vortex configurations within elements during reversal are seen to be affected by small changes in element corner shape. Similarly, small trapped domains and domain walls are observed to applied fields significantly larger than the coercive field and apparent magnetic saturation field, as determined by hysteresis loop measurements of arrays of elements. These are shown to have a dramatic effect on the character of the low-field magnetic hysteresis. Particles with long axis parallel to the [001] direction have large remanence and switching fields which also depend sensitively on end shape. The angular dependence of the switching field observed in these elements is contrasted to that of magnetization reversal by coherent rotation.