Giant magnetocaloric effect near room temperature in the off-stoichiometric Mn-Co-Ge alloy

TL;DR

This paper reports a record-high magnetocaloric effect near room temperature in an off-stoichiometric Mn-Co-Ge alloy, demonstrating its potential for magnetic refrigeration applications and addressing measurement challenges during phase transitions.

Contribution

It introduces an experimental protocol to accurately measure the magnetocaloric effect in sharp first-order transitions and reports the highest entropy change near room temperature in undoped Mn-Co-Ge alloys.

Findings

Peak entropy change of nearly 40 J/kg-K at 297 K

Refrigerant capacity of 270 J/kg between 293.5 K and 302.5 K

Protocol to avoid spurious peaks in measurements

Abstract

We report a giant magnetocaloric effect near room temperature in an off-stoichiometric Mn-Co-Ge alloy, across the magnetostructural transition. The isothermal entropy change accompanying this transition has a peak value of nearly 40 J/kg-K near 297 K and a refrigerant capacity of 270 J/kg with the hot end at 302.5 K and cold end at 293.5 K. We also present an experimental protocol to avoid spurious peaks in the magnetocaloric effect across a sharp first order magnetostructural transition, not confined to Mn-Co-Ge alone, where metastability during the transition could influence the measured magnetization and thus the estimated entropy change. The estimated entropy change in the present off-stoichiometric Mn-Co-Ge alloy is possibly the highest reported value near room temperature in undoped Mn-Co-Ge alloys and underlines the potential of the alloy for technological applications in room temperature magnetic refrigeration.