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September, 2019

There is great interest in using magnetic materials that display magnetically driven thermal changes for the purposes of environmentally friendly refrigeration and air-conditioning. However, the performance of magnetocaloric cooling devices based on these materials has historically been uncompetitive because they require impractically large changes of magnetic field, and because most of these materials are brittle and crumble under operation. Here we overcome both the large-field and brittle-fracture issues by using moderate changes of hydrostatic pressure to reversibly drive giant caloric effects in the notoriously brittle magnetocaloric material MnCoGeB0.03. The resulting barocaloric effects compare favourably with other barocaloric materials that are magnetic. The inevitable fragmentation provides a large surface for heat exchange with the pressure transmitting medium, permitting good access to barocaloric effects for use in cooling devices.

Figure: Top, measurements of dQ/|dT| reveal that mechanical breakdown arises with thermal cycling (Q denotes heat). Bottom, pressure-driven thermal changes in MnCoGeB0.03T denotes temperature change).

A. Aznar, P. Lloveras, J.-Y. Kim, E. Stern-Taulats, M. Barrio, J. Ll. Tamarit, C.F. Sánchez-Valdés, J.L. Sánchez Llamazares, N. D. Mathur, and X. Moya, "Giant and reversible inverse barocaloric effects near room temperature in ferromagnetic MnCoGeB0.03", Advanced Materials 2019

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