(07A912) Phase evolution and magnetocaloric effect of melt-spun Mn_3Sn_(2-x)M_x (M= B, C; x= 0-0.5) ribbons

摘要

The effects of B and C substitution for Sn on phase components, Curie temperature T_C, and magnetocaloric effect of melt-spun Mn_3Sn_(2-x)M_x (M = B, C; x = 0—0.5) ribbons have been investigated. X-ray diffraction (XRD) results show that the main phase in the as-spun Mn_3Sn_(2-x)M_x (M=B, C; x = 0-0.5) ribbons is Mn_3Sn_2 of Ni_3Sn_2-type (Pnma). Minor Mn_2B (when x≥0.1) or Mn_5C_2 (when x > 0.1) secondary phase is formed, and their amounts increase with increasing B and C concentration, respectively. The Curie temperature T_c of these ribbons varies in the temperature range of 240—250 K. The peak values of the maximal magnetic entropy change, — ΔS_M~(max), are about 13.6—18.3 mJ/cm~3 K for B-substituted ribbons and 13.6-17.5 mJ/cm3 K for C-substituted ribbons, respectively, at a maximum applied field of 50 kOe. These values are about one fifth that of Gd (81.4 mJ/cm~3 K). However, the relatively broader temperature range of the half maximum of ΔS_M peak (~100K), low-cost and nontoxic elements still make Mn_3Sn_2-based ribbons the promising candidates for magnetic refrigeration applications close to room temperature.