Large magnetic entropy change in TbAl2 and (Tb0.4Gd0.6)Al2

Abstract

Rare-earth intermetallic compounds $({\mathrm{Tb}}_{\text{1−x}}{\mathrm{Gd}}_x){\mathrm{Al}}_{\mathrm{2}},$ have been successfully fabricated and characterized. Large magnetic entropy change, ${\mathrm{\Delta S}}_M,$ was observed in these alloys. The maximum ${\mathrm{-\Delta S}}_M\text{(=14.3\hspace{0.05em}}\mathrm{J/kg K})$ is achieved in the ${\mathrm{TbAl}}_{\mathrm{2}}$ alloy at its Curie temperature, $T_C\text{=105\hspace{0.05em}}\mathrm{K},$ with a 5 T magnetic field change. It is shown that the alloys are very soft magnetic alloys. The magnetic entropy change is thus completely reversible in the whole temperature range of 80–180 K. An interesting feature in $({\mathrm{Tb}}_{\text{1−x}}{\mathrm{Gd}}_x{\mathrm{)Al}}_{\mathrm{2}}$ compounds is that the Curie temperature can be easily shifted by tuning the composition. These alloys, therefore, appear to be an attractive material candidate for realizing the active magnetic regenerator magnetic refrigerator consisting of eight stages, as suggested by K. A. Gschneidner, Jr. and V. K. Percharsky. [Rare Earth: Science, Technology, and Applications III, edited by R. G. Bautista, C. O. Bounds, T. W. Ellis, and B. T. Kilbourn (The Minerals, Metals and Materials Society, 1997), p. 209.]