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

A giant magnetocaloric effect (ΔSmag) has been discovered in the Gd5(SixGe1−x)4 pseudobinary alloys, where x⩽0.5. For the temperature range between ∼50 and ∼280 K it exceeds the reversible (with respect to alternating magnetic field) ΔSmag 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 ΔSmag in Gd5(SixGe1−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 ∼30 to ∼276 K by adjusting the Si:Ge ratio without losing the giant magnetic entropy change.