Magnetic refrigeration material operating at a full temperature range required for hydrogen liquefaction

TLDR

Magnetic refrigeration is a promising technique for hydrogen liquefaction, yet practical use is limited by the absence of materials with large magnetic entropy change across the 20–77 K range required for liquefaction. We identified Er(Ho)Co₂-based alloys exhibiting a reversible giant magnetocaloric effect (ΔSₘ > 0.2 J cm⁻³ K⁻¹) over 20–77 K, making them suitable for sustainable MR cooling of hydrogen.

Abstract

Abstract Magnetic refrigeration (MR) is a key technique for hydrogen liquefaction. Although the MR has ideally higher performance than the conventional gas compression technique around the hydrogen liquefaction temperature, the lack of MR materials with high magnetic entropy change in a wide temperature range required for the hydrogen liquefaction is a bottle-neck for practical applications of MR cooling systems. Here, we show a series of materials with a giant magnetocaloric effect (MCE) in magnetic entropy change (-∆ S m > 0.2 J cm −3 K −1 ) in the Er(Ho)Co 2 -based compounds, suitable for operation in the full temperature range required for hydrogen liquefaction (20-77 K). We also demonstrate that the giant MCE becomes reversible, enabling sustainable use of the MR materials, by eliminating the magneto-structural phase transition that leads to deterioration of the MCE. This discovery can lead to the application of Er(Ho)Co 2 -based alloys for the hydrogen liquefaction using MR cooling technology for the future green fuel society.