Observation of enhanced exchange bias behavior in NiCoMnSb Heusler alloys

TL;DR

This study reports a significant enhancement of exchange bias in NiCoMnSb Heusler alloys due to phase coexistence, with the maximum exchange bias field reaching 480 Oe at 3K, nearly doubling previous records.

Contribution

It demonstrates a substantial increase in exchange bias in NiCoMnSb alloys through Co substitution, highlighting the role of phase coexistence and antiferromagnetic coupling.

Findings

Maximum exchange bias of 480 Oe at 3K in x=5 alloy.

Exchange bias increases with Co concentration.

Phase coexistence explains the enhanced exchange bias.

Abstract

We report the observation of large exchange bias in Ni50-xCoxMn38Sb12 Heusler alloys with x=0, 2, 3, 4, 5, which is attributed to the coexistence of ferromagnetic and antiferromagnetic phases in the martensitic phase. The phase coexistence is possibly due to the supercooling of the high temperature ferromagnetic phase and the predominant antiferromagnetic component in the martensitic phase. The presence of exchange bias is well supported by the observation of training effect. The exchange bias field increases with Co concentration. The maximum value of 480 Oe at T=3K is observed in x=5 after field cooling in 50 kOe, which is almost double the highest value reported so far in any Heusler alloy system. Increase in the antiferromagnetic coupling after Co substitution is found to be responsible for the increase in the exchange bias.