Large barocaloric effect with high pressure-driving efficiency in hexagonal MnNi0.77Fe0.23Ge alloy

TL;DR

This study demonstrates that hydrostatic pressure can effectively tune the magnetostructural transition in a MnNi0.77Fe0.23Ge alloy, resulting in a large barocaloric effect suitable for solid-state cooling applications.

Contribution

It reveals a highly pressure-sensitive magnetostructural transition with a giant shift rate and significant entropy change, advancing the understanding of barocaloric effects in hexagonal MMX alloys.

Findings

Giant shift rate of -151 K GPa-1 in transition temperature

Large magnetic entropy change of -23 J kg-1 K-1 under 5 T field

Temperature span of 30 K for caloric effect

Abstract

The hydrostatic pressure is expected to be an effective knob to tune the magnetostructural phase transitions of hexagonal MMX alloy. In this study, magnetization measurements under hydrostatic pressure were performed on a MMX martensitic MnNi0.77Fe0.23Ge alloy. The magnetostructural transition temperature can be efficiently tuned to lower temperatures by applying moderate pressures, with a giant shift rate of -151 K GPa-1. A temperature span of 30 K is obtained under the pressure, within which a large magnetic entropy change of -23 J kg-1 K-1 in a field change of 5 T is induced by the mechanical energy gain due to the large volume change. Meanwhile, a decoupling of structural and magnetic transitions is observed at low temperatures when the martensitic transition temperature is lower than the Curie temperature. These results show a multi-parameter tunable caloric effect that benefits the solid-state cooling.