Tunable magnetic regenerator alloys with a giant magnetocaloric effect for magnetic refrigeration from ∼20 to ∼290 K

A giant magnetocaloric effect ${\mathrm{(\Delta S}}_{\mathrm{mag}})$ has been discovered in the ${\mathrm{Gd}}_{\mathrm{5}}({\mathrm{Si}}_x{\mathrm{Ge}}_{\text{1−x}}{)}_4$ pseudobinary alloys, where $\text{x⩽0.5.}$ For the temperature range between $\text{∼50}$ and $\text{∼280\hspace{0.17em}}\mathrm{K}$ it exceeds the reversible (with respect to alternating magnetic field) ${\mathrm{\Delta S}}_{\mathrm{mag}}$ for any known magnetic refrigerant material at the corresponding Curie temperature by a factor of 2–10. The two most striking features of this alloy system are: (1) the first order phase transformation, which brings about the large ${\mathrm{\Delta S}}_{\mathrm{mag}}$ in ${\mathrm{Gd}}_{\mathrm{5}}({\mathrm{Si}}_x{\mathrm{Ge}}_{\text{1−x}}{)}_4,$ is reversible with respect to alternating magnetic field, i.e., the giant magnetocaloric effect can be utilized in an active magnetic regenerator magnetic refrigerator; and (2) the ordering temperature is tunable from $\text{∼30}$ to $\text{∼276\hspace{0.17em}}\mathrm{K}$ by adjusting the Si:Ge ratio without losing the giant magnetic entropy change.