Influence of Sn substitution for Co in RCo_2 (R = Gd, Tb, Dy) alloys on the structure and magnetocaloric effect

摘要

The phases and the magnetocaloric effect in the alloys R(Co_(1-x)Sn_x)_2 with x = 0, 0.025, 0.050, 0.075, and 0.100 were investigated by X-ray diffraction analysis and magnetization measurement. The substitution of Sn in RCo_2 is limited. The cubic MgCu_2-type structure for the alloys of RCo_2 was confirmed by X-ray powder diffraction and the remaining alloys mainly consisted of the RCo_2 phase, along with some RCo_3 and R_5Sn_3 impurity phases. The impurity phases increase with the increase of Sn content. The T_c of the alloys is not very sensitive to the Sn substitution for Dy(Co_(1-x)Sn_x)_2 and Tb(Co_(1-x)Sn_x)_2, whereas in Gd(Co_(1-x)Sn_x)_2, the Curie temperatures significantly increase. The maximum magnetic entropy changes in the alloys Dy(Co_(1-x)Sn_x)_2 (x = 0, 0.025, 0.050, 0.075) are 5.78, 5.43, 3.88, and 2.98 J·kg~(-1)·K~(-1), respectively, and those in the Tb(Co_(1-x)Sn_x)_2 (x = 0, 0.025) are 3.44, and 2.29 J·kg~(-1)·K~(-1) respectively in the applied field change of 0-2.0 T.