Giant inverse magnetocaloric effect near room temperature in Co substituted NiMnSb Heusler alloys

TL;DR

This study demonstrates a significant enhancement of the magnetocaloric effect near room temperature in Co-substituted NiMnSb Heusler alloys, with a maximum entropy change of 34 Jkg-1K-1 at 262 K, driven by magnetic transition changes.

Contribution

It reveals how Co substitution in NiMnSb alloys induces a giant magnetocaloric effect near room temperature, advancing magnetic cooling materials.

Findings

Maximum magnetic entropy change of 34 Jkg-1K-1 at 262 K for x=5

Martensitic transition temperature decreases with Co content

Giant MCE linked to reverse martensitic transition

Abstract

The effect of Co on the structural, magnetic and magnetocaloric effect (MCE) of Ni50-xCoxMn38Sb12 (x=0,2,3,4,5) Heusler alloys was studied. Using x-ray diffraction, we show the evolution of the martensitic phase from the austenite phase. The martensitic transition temperature is found to decrease monotonically with Co concentration. Remarkable enhancement of MCE is observed near room temperature upon Co substitution. The maximum magnetic entropy change of 34 Jkg-1K-1 was achieved in x=5 at 262 K in a field of 50 kOe and a value of 29 Jkg-1K-1 found near room temperature. The significant increase in the magnetization associated with the reverse martensitic transition is responsible for the giant MCE in these compounds.