Investigation of the High Efficient GM Refrigerator with the High Entropy Magnetic Regenerator Materials in the He Temperature Range

Abstract

In the present paper we have investigated the method to produce the high efficient regenerator by using the magnetic regenerator materials in the He temperature range. These days, the magnetic materials with low magnetic phase transition temperature T_c are thought to be the promising regenerator materials below 10K. However, the very sharp peak of the magnetic specific heat C_J appears near T_c in the temperature dependence curve and, moreover, its value is almost same order of the value of the specific heat of the He gas. Therefore, it is difficult to make the efficient regenerator by using only a kind of a magnetic material. In the present investigation, in order to produce the highly efficient regenerator, we selected two kinds of magnetic materials whose T_c's are different, and produced the layered type regenerator in which the magnetic material with the high T_c piled up that with the low T_c. In the computer simulation and experiment it is verified that the layered type regenerator (Er_0.9Yb_0.1Ni+Er₃Ni) is more efficient than that with only Er₃Ni. Moreover, we have made new double-layered regenerator with Er_0.9Yb_0.1Ni and Er₃Co, where T_c of Er₃Co is almost twice T_c of Er₃Ni. Applying this regenerator to the GM refrigerator, we have succeeded to obtain the fairly large refrigeration capacity of 1.05W at 4.2K. Finally, on the basis of the above results, we discussed the direction of the development of the magnetic regenerator in future.