Study on Gd-Si-Ge alloys using Chinese Gd.

To evaluate the possibility of using Gd-Si-Ge alloys in magnetic refrigerators, samples of Gd-Si-Ge alloys were made of Chinese Gd. The magnetocaloric effect of samples was estimated by the magnetic entropy change, which were calculated from the M-H curves according to a Maxwell relation. The first order phase transformation was destroyed due to the impurities in the commercial Gd, so that no giant magnetocaloric effect was found. The samples made of purified Gd exhibit a first order phase transformation, and the magnetic entropy change was basically consistent with the published data of the AMES laboratory, USA. These materials were then used in a reciprocating prototype of magnetic refrigerator, and the result of the experiment was comparable with that using Gd. This work proves that Gd-Si-Ge alloys made of Chinese Gd can be utilized in magnetic refrigerators.