Domain wall dynamics in GaMnAsP films with perpendicular anisotropy

Abstract

Dynamics of domain wall (DW) nucleation, relaxation and switching is studied in a series of GaMnAsP films with anisotropy perpendicular to the film plane using ac susceptibility measurements. Measurements of dc and ac magnetization along the [001] crystal axis (the easy axis of GaMnAsP film) were performed by a superconducting quantum interference device (SQUID). The ac driving field was applied at various frequencies, from 0.1 Hz to 1000 Hz at an amplitude of 3.77 Oe. Characteristic dynamic modes in the ac spectra were mapped in all GaMnAsP films near the Curie temperature T_C, where the coercive field is comparable to the ac driving field. More significantly, we were able to identify DW relaxation, sliding, and switching from Cole-Cole plots. We found that DW segmental relaxation becomes dominant in GaMnAsP films with higher P concentration, where the coercive fields are enlarged as P concentration increases.