Giant magnetocaloric effect in the (Mn,Fe)NiSi-system

TL;DR

This paper reports a new Mn-Fe-Ni-Si-Al material exhibiting a giant magnetocaloric effect at room temperature, achieved through phase competition and magnetic interactions, promising for energy-efficient magnetic refrigeration.

Contribution

It introduces a novel material with an exceptionally large MCE at room temperature and elucidates the microscopic mechanism behind this effect using experimental and theoretical approaches.

Findings

Large isothermal entropy change at room temperature

Phase competition between hexagonal and orthorhombic structures

Magnetic properties driven by phase coexistence

Abstract

The search for energy-efficient and environmentally friendly cooling technologies is a key driver for the development of magnetic refrigeration based on the magnetocaloric effect (MCE). This phenomenon arises from the interplay between magnetic and lattice degrees of freedom that is strong in certain materials, leading to a change in temperature upon application or removal of a magnetic field. Here we report on a new material, Mn$_{1-x}$Fe$_x$NiSi$_{0.95}$Al$_{0.05}$, with an exceptionally large isothermal entropy at room temperature. By combining experimental and theoretical methods we outline the microscopic mechanism behind the large MCE in this material. It is demonstrated that the competition between the Ni$_2$In-type hexagonal phase and the MnNiSi-type orthorhombic phase, that coexist in this system, combined with the distinctly different magnetic properties of these phases, is a key parameter for the functionality of this material for magnetic cooling.