Effect of Co and Fe on the inverse magnetocaloric properties of Ni-Mn-Sn

TL;DR

This study investigates how substituting Co and Fe into Ni-Mn-Sn Heusler alloys affects their inverse magnetocaloric properties, revealing that Fe can enhance the entropy change while Co generally decreases it.

Contribution

It provides new insights into how Co and Fe substitutions modify the magnetocaloric effect in Ni-Mn-Sn alloys, highlighting the potential for tuning their properties for applications.

Findings

Fe substitution at 3 at% increases entropy change to ~30 Jkg$^{-1}$K$^{-1}$

Co substitution decreases the magnetocaloric effect at certain concentrations

Both Fe and Co reduce the martensitic transition temperature

Abstract

At certain compositions Ni-Mn-$X$ Heusler alloys ($X$: group IIIA-VA elements) undergo martensitic transformations, and many of them exhibit inverse magnetocaloric effects. In alloys where $X$ is Sn, the isothermal entropy change is largest among the Heusler alloys, particularly in Ni$_{50}$Mn$_{37}$Sn$_{13}$ where it reaches a value of 20 Jkg$^{-1}$K$^{-1}$ for a field of 5T. We substitute Ni with Fe and Co in this alloy, each in amounts of 1 at% and 3 at% to perturb the electronic concentration and examine the resulting changes in the magnetocaloric properties. Increasing both Fe and Co concentrations causes the martensitic transition temperature to decrease, whereby the substitution by Co at both compositions or substituting 1 at% Fe leads to a decrease in the magnetocaloric effect. On the other hand, the magnetocaloric effect in the alloy with 3 at% Fe leads to an increase in the value of the entropy change to about 30 Jkg$^{-1}$K$^{-1}$ at 5T.