High field, high frequency magnetic dynamics of narrow thin-film magnetic multilayer stripes

Abstract

The dynamic surface magnetic response and flux propagation in arrays of multilayer magnetic thin-film stripes subject to high frequency magnetic fields has been studied using scanning Kerr imaging and a high frequency permeameter respectively. Scanning Kerr Images of the regions of surface response to a uniform oscillating magnetic field of up to 2 Oc between 1 and 50 MHz identify the domain state and surface permeability of the multilayer films. Transitions among the expected easy-axis laminated, hard axis, closure domain and a new complex domain state are observed as the total and magnetic layer thicknesses, stripe widths and field history are changed. As expected, the high frequency magnetic response of single layer films is dominated by magnetization rotation at low field, while closure domain wall motion becomes significant above the coercivity. Easy-axis domain state multilayer films, in narrow structures those films with magnetic layers a few hundred Ångströms thick or less, exhibit a uniform high permeability over the entire surface of the film. The dynamics of the new complex domain pattern seen in narrow multilayer films with thicker magnetic layers is complicated, with a blotchy, hysteretic magnetic response from the center of the strip and a immobile, mostly hard-axis oriented region along the edge. © 1992.