Performance Assessment and Layer Fraction Optimization of Gd-Y Multilayer Regenerators for Near Room-Temperature Magnetic Cooling

An experimental and numerical assessment of multilayer active magnetic regenerators (AMR) composed of gadolinium (Gd) and gadolinium-yttrium (Gd-Y) alloys (Gd97.34Y2.66, Gd95.98Y4.02 and Gd94.79Y5.21) is presented. First, by calculating the adiabatic temperature change and the isothermal entropy change from the experimental data for the above materials, we show that, with reasonable accuracy for engineering design purposes, these properties can be determined by shifting the properties of pure Gd to the Curie temperature of the Gd-Y alloy - a common but not yet validated assumption in the design of Gd-Y AMRs with a low Y content. Next, we show that the optimal Gd-Y layer fraction in multilayer AMRs can be determined using the figure of merit known as the material refrigerant capacity (RC), which agrees well with the results from a more complex one-dimensional thermal non-equilibrium porous medium AMR model. Finally, the performance of the latter model is verified against the experimental cooling power data for two- and three-layer Gd-Y regenerators at temperature spans of 25, 30 and 35 K.