Verification of first-order magnetic phase transition in single crystal iron films

Abstract

In a recent publication [1] we reported observations of a first order transition of the orientation of the magnetization in single crystal iron films grown on GaAs substrates by molecular beam epitaxy. We have extended our observations of these samples, studying both the magnetization and the ferromagnetic resonance (FMR) in the vicinity of the transition. We find excellent agreement between the observed and the calculated values for the magnetization and the FMR in the transition region using parameters determined from FMR at magnetic fields large enough to quasi-align the magnetization with the applied magnetic field. Hysteresis is noted in both the magnetization and the FMR at the transition verifying the predicted first order nature of the transition. An examination of the FMR lineshape and the component of the magnetization along the [110] direction in the transition region indicate that a small but finite field change is required to propagate the phase transition through the sample. We suggest that this sluggishness is due to domain wall pinning induced by the presence of strain-relaxing dislocations.