Enhancement of the magnetocaloric effect in composites: Experimental validation

Recent calculations have shown that the refrigerant capacity (RC) of magnetic refrigerants can be enhanced using multiphase materials or composites, which expand the temperature range over which a significant magnetic entropy change can be obtained. This work is a systematic experimental validation of the improvement of RC (RCI) using layered composites comprised of two Fe88−2yCoyNiyZr7B4Cu1 amorphous alloy constituents, with y=8.25 and y=11 compositions. RCI has a nonmonotonic dependence on the applied magnetic field H and the fraction x of the two constituent phases. In contrast to common assumptions, the composite has a smaller RCI than its constituent phases for small values of H and x, and there are critical values of each for which RCI is maximized. This work demonstrates the outstanding agreement between the experimental results and the continuous curves predicted by numerical calculations, indicating that this approach can be used to design magnetic refrigerant materials with enhanced magnetocaloric response for moderate magnetic fields.