Dynamical signature of a domain phase transition in a perpendicularly-magnetized ultrathin film

TL;DR

This study investigates the dynamic behavior of domain phases in ultrathin Fe/Ni/W(110) films during a phase transition, revealing slow relaxation linked to defect removal and domain rearrangement.

Contribution

It provides the first dynamical observation of the phase transition from a disordered to an ordered stripe phase in ultrathin magnetic films.

Findings

Susceptibility peak relaxes slowly with temperature

Peak temperature increases with slower heating rate

Relaxation dynamics match defect removal and domain rearrangement models

Abstract

Domain phases in ultrathin Fe/Ni/W(110) films with perpendicular anisotropy have been studied using the ac magnetic susceptibility. Dynamics on time scales of minutes to hours were probed by quenching the system from high temperature to the stripe phase region, and varying the constant rate of temperature increase as the susceptibility traces were measured. The entire susceptibility peak is observed to relax slowly along the temperature axis, with the peak temperature increasing as the rate of heating is decreased. This is precisely opposite to what would happen if this slow relaxation was driven by changes in the domain density within the stripe phase. The data are instead consistent with a simple model for the removal of a significant density of pattern defects and curvature trapped in the quench from high temperature. A quantitative analysis confirms that the relaxation dynamics are consistent with the mesoscopic rearrangement of domains required to remove pattern defects, and that the experiment constitutes a "dynamical" observation of the phase transition from a high temperature, positionally disordered phase to the low temperature, ordered stripe phase.