Abstract
We study the barocaloric effect (BCE) in the geometrically frustrated antiferromagnet across the Néel transition temperature. Experimentally, we find a larger barocaloric entropy change by a factor of 1.6 than that recently discovered in the isostructural antiperovskite despite significantly greater magnetovolume coupling in . By fitting experimental data to theory, we show that the larger BCE of originates from multisite exchange interactions amongst the local Mn magnetic moments and their coupling with itinerant electron spins. Using this framework, we discuss the route to maximize the BCE in the wider family.
- Received 12 June 2018
- Revised 28 September 2018
DOI:https://doi.org/10.1103/PhysRevX.8.041035
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Solid-state caloric cooling offers opportunities for more efficient refrigeration without the need for environmentally harmful chemicals. Magnetocalorics are the most studied alternative but rely on expensive permanent magnets. Far less studied are barocalorics, which control temperature with just an application of mechanical pressure. Recent experiments have shown that the material has a giant barocaloric effect (BCE). Here we report an unexpectedly large BCE in the related material , exceeding by almost 200%. By modeling the behavior of both materials, we provide a framework to understand these improved properties and also pave the way for an informed search for even larger BCEs in the wider family of Mn-antiperovskite materials.
The giant BCE of arises from the underlying magnetic frustration, where individual magnetic interactions cannot all be satisfied simultaneously. This causes large volume and caloric changes at the magnetic transition. is known to have a significantly smaller volume change at its magnetic transition, however, despite this, our results show that the associated caloric changes are larger. Our theoretical model reveals that magnetic interactions occur between multiple sites in the crystal structure, and these interactions increase the caloric change at the transition in , thus explaining the larger BCE.
Our theoretical framework offers a guide to finding yet-larger effects in the chemically flexible family of materials, where the site may take numerous different elements. Therefore, we anticipate that our results will stimulate further research into improving the promising BCE in these materials.