Strain energy enhanced room-temperature magnetocaloric effect in second-order magnetic transition materials

TL;DR

This study demonstrates that introducing strain energy into second-order magnetic transition materials significantly enhances their room-temperature magnetocaloric effect, offering a promising environmentally friendly approach for magnetic refrigeration.

Contribution

It reveals that strain energy can be used to substantially improve magnetic entropy change in second-order magnetic transition materials, demonstrated in Mn5Ge3.

Findings

60% increase in magnetic entropy change at 300K

Strain energy induces lattice deformation enhancing magnetization

Experimental and Monte Carlo results confirm the strain-induced enhancement

Abstract

Large magnetic entropy change (deltaSM) can realize a prominent heat transformation under the magnetic field and directly strengthen the efficacy of the magnetocaloric effect, which provides a pioneering environmentally friendly solid-state strategy to improve refrigeration capacities and efficiencies. The second-order magnetic transition (SOMT) materials have broader deltaSM peaks without thermal hysteresis compared with most first-order magnetic transition materials, making them highly attractive in magnetic refrigeration, especially in the room temperature range. Here, we report a significant enhancement of deltaSM at room temperature in single-crystal Mn5Ge3. In this SOMT system, we realize a 60% improvement of -deltaSM from 3.5 J/kgK to 5.6 J/kgK at T = 300K. This considerable enhancement of deltaSM is achieved by intentionally introducing strain energy through high-pressure constrained deformation. Both experimental results and Monte Carlo simulations demonstrate that the enhancement of deltaSM originates from the microscopic strain and lattice deformation induced by strain energy after deformation. This strain energy will reconstruct the energy landscape of this ferromagnetic system and enhance magnetization, resulting in a giant intensity of magnetocaloric responses. Our findings provide an approach to increase magnetic entropy change and may give fresh ideas for exploring advanced magnetocaloric materials.