Magnetocaloric Effect, Specific Heat, and Entropy of Iron-Substituted Gadolinium Gallium Garnets Gd3(Ga1-xFex)5O12

A series of Gd-x(Ga1-xFex)(5)O-12 (GGIG) compounds for magnetic refrigerants were characterized by magnetization and specific heat measurements For comparison, the base compound gadolinium gallium garnet (GGG) was also measured From the magnetization measurements: the entropy change by external magnetic field was confirmed to be enhanced by the addition of iron, as previously reported by the National Institute of Standards and Technology (NIST) group. the specific heat data obtained in various magnetic fields enabled the establishment of temperature entropy (T-S) diagrams, which are essential for thermal cycle analysis. It has been shown that GGIGs with high iron content have a large specific heat in zero field, and are suitable for regenerative thermal cycle. (C) 2009 The Japan Society of Applied Physics