Enhanced magnetocaloric effect in rare-earth aluminum-based magnetic materials for hydrogen liquefaction

Efficient magnetocaloric materials are essential for the liquefaction of hydrogen, a clean energy carrier that requires cryogenic temperatures. Traditional refrigeration methods for hydrogen liquefaction are energy-intensive, making the search for alternative technologies critical. This study explores the magnetocaloric properties of Er_1-xHo_xAl₂ compounds, focusing on the effects of Ho doping. Using a combination of density functional theory calculations and experimental measurements, we systematically examine how Ho incorporation influences the electronic structure, magnetic properties, and magnetocaloric effect (MCE) of these materials. Our findings indicate that Ho doping effectively adjusts the Curie temperature to align closely with the hydrogen liquefaction point. Theoretical calculations reveal significant modifications in the electronic structure due to Ho doping, which enhance ferromagnetic interactions. Experimentally, Er_0.8Ho_0.2Al₂ and Er_0.6Ho_0.4Al₂ exhibit maximum magnetic entropy changes of 16.1 J/kg K and 14.7 J/kg K, under a magnetic field change of 0–2 T. The corresponding values for refrigeration capacity (RC) are 150.9 J/kg, and 183.6 J/kg, respectively. These results highlight the potential of Er_1-xHo_xAl₂ compounds as efficient magnetocaloric materials for hydrogen liquefaction, offering substantial performance improvements under low magnetic fields.