Magnetocaloric effect over a wide temperature range in GdxHo3−xAl2 compounds with successive magnetic transitions

- The working temperature range is expanded by substituting Ho with Gd atoms.
- GdxHo3−xAl2 (x = 1.0-2.5) exhibit nearly constant ΔSM in 100-250 K.
- A gaint RC is obtained in GdHo2Al2 due to partial overlap of successive ΔSM peaks.
- GdHo2Al2 is good candidate for magnetic refrigeration of natural gas liquefaction.

The GdxHo3−xAl2 (x = 0.5-2.5) compounds undergo two successive magnetic transitions: a second-order magnetic transition from paramagnetism (PM) to ferromagnetism (FM) around TC followed by a FM to ferrimagnetism (FIM)-like transition at Tt. The TC increases linearly with the increase of Gd content due to the de Gennes factor of Gd being larger than that of Ho, while the Tt remains nearly constant around 45 K independent of the variation of Gd content. The working temperature range is expanded by substituting Ho with Gd atoms due to the higher transition temperature of Gd3Al2 and the different composition dependence of successive magnetic transitions, and thus leading to an enhanced refrigerant capacity (RC). For a relatively low field change of 2 T, a giant RC value of 272 J/kg with a wide working temperature range of ∼80 K is obtained for x = 1.0 compound due to the partial overlap of successive ΔSM peaks. This is probably the largest RC value so far reported in the temperature range of liquid natural gas (111 K). Consequently, the large ΔSM and giant RC suggest that GdxHo3−xAl2 compounds could be good candidates of magnetic refrigerants in a wide temperature range.