Antiferromagnetic-ferromagnetic phase domain development in nanopatterned FeRh islands

TL;DR

This study visualizes how magnetic phase domains in nanopatterned FeRh islands develop during phase transition, revealing size-dependent behaviors and the impact of fabrication-induced disorder on transition temperature.

Contribution

It provides direct imaging of phase domain evolution in FeRh nanostructures and links size and edge effects to changes in transition behavior and temperature.

Findings

Domain development proceeds via nucleation, growth, and merging in larger islands.

Smaller islands show stunted growth and reduced transition temperature.

Edge disorder from fabrication influences the phase transition temperature.

Abstract

The antiferromagnetic to ferromagnetic phase transition in B2-ordered FeRh is imaged in laterally confined nanopatterned islands using photoemission electron microscopy with x-ray magnetic circular dichroism contrast. The resulting magnetic images directly detail the progression in the shape and size of the FM phase domains during heating and cooling through the transition. In 5 um square islands this domain development during heating is shown to proceed in three distinct modes: nucleation, growth, and merging, each with subsequently greater energy costs. In 0.5 um islands, which are smaller than the typical final domain size, the growth mode is stunted and the transition temperature was found to be reduced by 20 K. The modification to the transition temperature is found by high resolution scanning transmission electron microscopy to be due to a 100 nm chemically disordered edge grain present as a result of ion implantation damage during the patterning. FeRh has unique possibilities for magnetic memory applications; the inevitable changes to its magnetic properties due to subtractive nanofabrication will need to be addressed in future work in order to progress from sheet films to suitable patterned devices.