Phase Coexistence and Kinetic Arrest in the Magnetostructural Transition of the Ordered Alloy FeRh

David J Keavney,Yongseong Choi,Dario Arena,Philip J Ryan,Martin V Holt,Eric E Fullerton,Jong-Woo Kim,Vojtěch Uhlíř

doi:10.1038/s41598-018-20101-0

Abstract

In materials where two or more ordering degrees of freedom are closely matched in their free energies, coupling between them, or multiferroic behavior can occur. These phenomena can produce a very rich phase behavior, as well as emergent phases that offer useful properties and opportunities to reveal novel phenomena in phase transitions. The ordered alloy FeRh undergoes an antiferromagnetic to ferromagnetic phase transition at ~375 K, which illustrates the interplay between structural and magnetic order mediated by a delicate energy balance between two configurations. We have examined this transition using a combination of high-resolution x-ray structural and magnetic imaging and comprehensive x-ray magnetic circular dichroism spectroscopy. We find that the transition proceeds via a defect-driven domain nucleation and growth mechanism, with significant return point memory in both the structural and magnetic domain configurations. The domains show evidence of inhibited growth after nucleation, resulting in a quasi-2nd order temperature behavior.

Highlights

Of interest for magnetic storage applications, due to the potential to use the high-temperature FM phase as a write-assist layer for heat-assisted magnetic recording or the AFM phase for memory elements
Spatially resolved studies of the magnetic transition using X-ray photoemission electron microscopy (X-photoemission electron microscope (PEEM)) have been reported, in which a domain growth and nucleation process were observed[9,19,20]
We have examined the evolution of the average structural and magnetic order employing combined x-ray diffraction (XRD) with Fe K, and Rh L2 edge x-ray magnetic circular dichroism (XMCD) spectroscopy in which the same experimental set up is used, providing common thermometry

Summary

Introduction

Of interest for magnetic storage applications, due to the potential to use the high-temperature FM phase as a write-assist layer for heat-assisted magnetic recording or the AFM phase for memory elements. Spatially resolved studies of the magnetic transition using X-ray photoemission electron microscopy (X-PEEM) have been reported, in which a domain growth and nucleation process were observed[9,19,20]. Studies of the structural domain evolution, and especially coupled magnetic and structural experiments have been less common, owing to a lack of real space probes of lattice parameter with adequate spatial resolution. We apply multimodal nanoscale imaging to examine the domain morphology in both the structural and magnetic transitions, coupled with wide area x-ray magnetic circular dichroism (XMCD) spectroscopy to track the correlation between the structure and the Rh and Fe moments in epitaxial FeRh(001) films. The magnetic transition mirrors the nucleation and growth model, with large final domains in the high temperature phase resulting from coalescence

Methods

Results

Conclusion