Correlating the properties of near-room-temperature first- and second-order magnetocaloric materials

Abstract

Several magnetocaloric materials have been proposed since the discovery of the Giant Magnetocaloric Effect. Although some have great potential as magnetocaloric refrigerants or working materials in thermomagnetic motors/generators, only a few have been tested experimentally or had their properties incorporated into validated mathematical models. While experiments are limited by material costs and specialized equipment to determine magnetic field-dependent properties such as specific heat capacity and magnetization, the development of correlation methods must ensure data quality and resolution over a wide range of conditions to reduce interpolations errors. Aiming to keep the number of baseline experimental data points at a minimum, we propose a fitting procedure to correlate thermomagnetic quantities (i.e., isofield specific heat capacity, magnetization and isothermal entropy change) that is accurate at intermediate (i.e., not directly measured) temperatures and applied magnetic fields. The method has been applied to different first-order materials (La(Fe,Mn,Si)13Hy and MnFePxAs1−x) and second-order materials (Gd and Gd100−xYx) with a good reproducibility of the isofield specific heat capacity, entropy–temperature diagram, adiabatic temperature change and magnetization behavior around room temperature at applied fields between 0 and 2 T.