Experimental application study of the Er_0.5Tm_0.5CuAl magnetocaloric material in the liquid helium temperature region refrigerator

Based on the monodisperse technology combined with the in-situ annealing device in this paper, the process is optimized to prepare Er_0.5Tm_0.5CuAl microspheres with uniform particle size, high sphericity, and large magnetocaloric effect in the application of the liquid helium temperature region, and the application characteristics are verified by using an independently constructed composite GM magnetic refrigerator. A multilayer active magnetic reheater is further constructed and temperature-matched is used to obtain wide temperature span. Finally, the effects of the Er_0.5Tm_0.5CuAl microspheres filling mass, particle size, operating frequency and refrigeration mode on the no-load temperature and cooling capacity of the composite GM magnetic refrigerator are described in detail. The experimental results demonstrate that the filling mass of Er_0.5Tm_0.5CuAl microsphere is 40 g, the particle size of the microsphere is 0.2∼0.4 mm, and the operating frequency is 0.5 Hz, Er_0.5Tm_0.5CuAl in the combined GM magnetic refrigeration mode exhibits a minimum no-load temperature and cooling capacity of 3.22 K and 0.76 W respectively. An improvement of cooling capacity is 20.6 %, compared to pure GM refrigeration mode. Furthermore, when compared to full HoCu₂ in pure GM refrigeration mode, the improvement of cooling capacity is 22.6 %. The results show that the composite GM magnetic refrigeration plays a significant role in improving the refrigeration effect of the GM refrigerator, which also provides a valuable reference for the experimental application of other magnetic refrigeration materials in the liquid helium temperature region on the composite GM magnetic refrigerator.