A permanent magnet magneto-refrigerator study on using Gd/Gd-Si-Ge/Gd-Si-Ge-Ga alloys.

A detailed study on a room temperature magnetic refrigerator using these alloys with a permanent magnet has been carried out. Gd-Si-Ge system alloys were prepared by using the Gd with purity of 99.9 wt%. The permanent magnet was shaped as a cylinder in which an uniform magnetic field is 1.4 T. The two beds of this reciprocating magnetic refrigerator were loaded with about 1 kg Gd-Si-Ge and Gd-Si-Ge-Ga. A temperature span of 25 K was reached when the temperature of the environment was about 298 K. If the alloys are short of Ga, less temperature span can be reached at the same temperature. For this phenomenon it seems likely that this material did not work in an optimal temperature range. To increase the running speed, the authors try to enhance the heat transfer of the material with less loss of magnetocaloric effect. It is expected to increase cooling power output by about 3-5 times.