A coupling of martensitic and metamagnetic transitions with collective magneto-volume and table-like magnetocaloric effects

TL;DR

This paper reports on the discovery of coupled magnetic and structural phase transitions in MnNi0.8Fe0.2Ge alloy, leading to unique magneto-volume and magnetocaloric effects with potential cooling applications.

Contribution

It introduces a novel coupling of martensitic and metamagnetic transitions resulting in combined magneto-volume and magnetocaloric effects in a single alloy.

Findings

Magnetic and structural phase transitions are coupled in the alloy.

The magnetocaloric effect has a wide temperature range near room temperature.

The alloy exhibits low hysteresis and high refrigerant capacity.

Abstract

A coupling of the first-order paramagnetic-to-induced-ferromagnetic martensitic and the second-order antiferromagnetic-to-ferromagnetic metamagnetic transitions was found in MnNi0.8Fe0.2Ge alloy. Based on the coupling, a magneto-volume effect driven by the martensitic transition and a table-like magnetocaloric effect generated by the successive magnetic phase transitions arise collectively. By using the magneto-volume effect, the internal pressure stress in the volume-expansion martensitic transition was determined at 350 MPa. The magnetocaloric effect, with a wide working temperature range of 26 K around room temperature, shows a small hysteresis loss (5 J/kg) and a large net refrigerant capacity (157 J/kg).