Magnetization reversal in Fe80B15Si5 metallic glass with large uniaxial magnetostrictive anisotropy

Abstract

Several experiments are described in which the mode of magnetization reversal of Fe80B15Si5 metallic glass ribbons with a large uniaxial magnetostrictive anisotropy is investigated. Although theoretically possible, magnetization is never found to occur by uniform spin rotation, but always by a domain wall process. The failure to observe coercivities approaching the theoretical limit, i.e., the anisotropy field, is ascribed to the presence of defects. These defects are of macroscopic size, as follows from the observed linearity between the coercive force and the square root of the applied stress at high stress levels. Magnetization reversal mostly starts by the detachment of probably one domain wall pinned at a defect, after which the wall propagates in a ’’Sixtus and Tonks way’’ through the ribbon. In the ’’saturated’’ state many of these residual walls are present, but the coercive force is determined by the weakest pinned wall. It is argued that metallic glass ribbons with a large uniaxial magnetostrictive anisotropy behave magnetically as single crystals.