Optimization of the refrigerant capacity in multiphase magnetocaloric materials

The refrigerant capacity $\left(RC\right)$ of magnetocaloric materials can be enhanced using multiphase materials or composites, which expand the temperature range over which a significant magnetic entropy change can be obtained. Numerical simulations show that by controlling the parameters of the composite (the fraction of the different phases and their Curie temperatures) improvements of $RC$ of $\sim 83\mathrm{\%}$ are possible. The maximum applied field plays a crucial, nonmonotonic, role in the optimization. As a proof of concept, it is shown that the combination of two ${\text{Fe}}_{88-2x}{\text{Co}}_x{\text{Ni}}_x{\text{Zr}}_7{\text{B}}_4{\text{Cu}}_1$ alloys produces an enhancement in $RC$ of $\sim 37\mathrm{\%}$ , making it $\sim 92\mathrm{\%}$ larger than that of ${\text{Gd}}_5{\text{Si}}_2{\text{Ge}}_{1.9}{\text{Fe}}_{0.1}$ .