Propagation of Transverse Domain Walls in Thin NiFeCo Films

Abstract

A new phenomenon of straight transverse domain walls has been observed in longitudinal propagation of walls in thin films. When the drive field is sufficiently large, the domain wall is observed to become nearly straight losing the jagged configuration typical of static transverse walls. If the drive field is rotated away from the longitudinal direction, the direction of propagation rotates the opposite way, but the wall remains straight. A model is suggested, relating the transverse component of external field near a skewed domain wall and the coherent rotation threshold in the material to the observed wall motion phenomena. The films were NiFeCo,1 nonmagnetostrictive, vacuum-evaporated on glass substrate, and 1000 to 3000 Å thick. The cobalt content was varied from 5% to 35%. The measured anisotropy, nucleation,1 and wall motion fields ranged, respectively, 6 to 40 Oe (Hk), 5 to 20 Oe (Hs), and 2 to 5 Oe (H0), the values in each case increasing with increasing cobalt content. Longitudinal domain wall velocities up to 5000 m/sec were observed. The velocity-drive field relation is strongly curved, lying between V=kH2 and V=kH3. The value of wall motion field (H0) does not appear to be directly related to the velocity-field curve, and H0 clearly does not act as subtraction from H.2 Wall velocity is sensitive to film thickness and composition, increasing with thickness and decreasing with increasing cobalt content.