Design of compensated ferrimagnetic Heusler alloys for giant tunable exchange bias

TL;DR

This study presents a rational design of compensated ferrimagnetic Heusler alloys exhibiting giant exchange bias and coercivity, with potential applications in magneto-electronic devices and rare-earth free magnets.

Contribution

The paper introduces a new design strategy for Heusler alloys with compensated ferrimagnetic states that achieve giant exchange bias near room temperature.

Findings

Giant exchange bias (>3 T) achieved in Mn-Pt-Ga alloys.

Large coercivity observed alongside exchange bias.

Design concept demonstrated on Mn-Fe-Ga with room-temperature transition.

Abstract

The discovery of materials with improved functionality can be accelerated by rational material design. Heusler compounds with tunable magnetic sublattices allow to implement this concept to achieve novel magnetic properties. Here, we have designed a family of Heusler alloys with a compensated ferrimagnetic state. In the vicinity of the compensation composition in Mn-Pt-Ga, a giant exchange bias (EB) of more than 3 T and a similarly large coercivity are established. The large exchange anisotropy originates from the exchange interaction between the compensated host and ferrimagnetic clusters that arise from intrinsic anti-site disorder. We demonstrate the applicability of our design concept on a second material, Mn-Fe-Ga, with a magnetic transition above room temperature, exemplifying the universality of the concept and the feasibility of room-temperature applications. Our study points to a new direction for novel magneto-electronic devices. At the same time it suggests a new route for realizing rare-earth free exchange-biased hard magnets, where the second quadrant magnetization can be stabilized by the exchange bias.