Cosubstitution in Ni-Mn-Sb Heusler compounds: Realization of room-temperature reversible magnetocaloric effect driven by second-order magnetic transition

Abstract

Materials showing reversible magnetocaloric effect near room temperature are desirable for green refrigeration technology. The compounds in the magnetic Heusler family displaying significant magnetocaloric effect driven by first-order magnetostructural transitions are in vogue. Comparatively, Heusler compounds undergoing second-order magnetic transition near room temperature are less explored in the context of discovering significant magnetocaloric effects, though they can offer certain advantages like less energy cost and hysteresis loss. Using density-functional theory in conjunction with model Hamiltonians, we explore potential room-temperature magnetocaloric materials near second-order magnetic transition by cosubstitution in the Ni-Mn-Sb family. Our investigation on two cosubstituted families, ${\mathrm{Ni}}_{2\ensuremath{-}x}{\mathrm{Fe}}_{x}{\mathrm{Mn}}_{1+z\ensuremath{-}y}{\mathrm{Cu}}_{y}{\mathrm{Sb}}_{1\ensuremath{-}z}$ and ${\mathrm{Ni}}_{2\ensuremath{-}x}{\mathrm{Co}}_{x}{\mathrm{Mn}}_{1+z\ensuremath{-}y}{\mathrm{Cu}}_{y}{\mathrm{Sb}}_{1\ensuremath{-}z}$, discovers significant numbers of compounds with second-order phase transition near room temperature exhibiting significant changes in magnetic entropy, comparable to that observed in the compounds showing inverse magnetocaloric effect near a first-order magnetostructural transition. We provide a systematic way to select potential reversible magnetocaloric compounds and analyze our results from their electronic structures and magnetic exchange interactions.