Rare earth-ruthenium intermetallic compounds have been developed for ues as regenerator materials in helium liquefaction Gifford-McMahon refrigerators. These compounds show characteristically lower magnetic transition temperatures than other rare earth intermetallic compounds. The refrigeration capacity of GM refrigerators has been remarkably improved by the use of Ho1·5Er1·5Ru spheres as regenerator materials at the temperature range below 5K. This material posseses a large heat capacity even under magnetic fields of 0.5T in such a temperature range. Spherical powders of these materials were produced by a simple method named the “low pressure jet method, ” which offers good sphericity powders with smooth surface. Nozzle clogging is a serious problem in this method, but we have overcome this problem by reducing gas elements such as oxygen, fluorine, from starting materials.
