National Institute for Materials Science (NIMS), Tohoku University and Japan Synchrotron Radiation Research Institute (JASRI) have developed a series of Er(Ho)Co2-based magnetic cooling alloys that can be used to efficiently cool hydrogen from 77 K to 20 K: its liquefaction temperature. These alloys show excellent cyclic durability and can be used to develop a high performance magnetic refrigeration system capable of low-cost hydrogen liquefaction—a key technology in achieving widespread use of the green fuel.