Tunable Magnetocaloric Properties of Gd-Based Alloys by Adding Tb and Doping Fe Elements

In this paper, the magnetocaloric properties of Gd(1−x)Tb(x) alloys were studied and the optimum composition was determined to be Gd(0.73)Tb(0.27). On the basis of Gd(0.73)Tb(0.27), the influence of different Fe-doping content was discussed and the effect of heat treatment was also investigated. The adiabatic temperature change (ΔT(ad)) obtained by the direct measurement method (under a low magnetic field of 1.2 T) and specific heat capacity calculation method (indirect measurement) was used to characterize the magnetocaloric properties of Gd(1−x)Tb(x)(x = 0~0.4) and (Gd(0.73)Tb(0.27))(1−y)Fe(y) (y = 0~0.15), and the isothermal magnetic entropy (ΔS(M)) was also used as a reference parameter for evaluating the magnetocaloric properties of samples together with ΔT(ad). In Gd(1−x)Tb(x) alloys, the Curie temperature (T(c)) decreased from 293 K (x = 0) to 257 K (x = 0.4) with increasing Tb content, and the Gd(0.73)Tb(0.27) alloy obtained the best adiabatic temperature change, which was ~3.5 K in a magnetic field up to 1.2 T (T(c) = 276 K). When the doping content of Fe increased from y = 0 to y = 0.15, the T(c) of (Gd(0.73)Tb(0.27))(1−y)Fe(y) (y = 0~0.15) alloys increased significantly from 276 K (y = 0) to 281 K (y = 0.15), and a good magnetocaloric effect was maintained. The annealing of alloys (Gd(0.73)Tb(0.27))(1−y)Fe(y) (y = 0~0.15) at 1073 K for 10 h resulted in an average increase of 0.3 K in the maximum adiabatic temperature change and a slight increase in T(c). This study is of great significance for the study of magnetic refrigeration materials with adjustable Curie temperature in a low magnetic field.