Thermal stability and magnetocaloric effect of the Gd_(65)Fe_(20)Al_(15-x)B_x (x=0-7) glassy ribbons

摘要

The thermal stability, magnetocaloric effect, and refrigeration capacity (RC) of Gd-based Gd_(65)Fe_(20)Al_(15-x)B_x (x=0-7) glassy ribbons have been investigated. A relatively wide supercooled liquid region ΔT_x(ΔT_x=T_x-T_g) (50-80 K) and large reduced glass transition temperature T_(rg)(T_(rg) = T_g/T_m) (>0.63) are found in Gd_(65)Fe_(20)Al_(15-x)B_x glassy ribbons. The distinctive glass transition and sharp crystalline events as well as large values of A Tx and Trg confirm the excellent glass forming ability of these alloys. The maximal magnetic entropy changes, -ΔS_M~(max), and RC values of the specimens are about 4.80-5.21 J/kg K and 700-800 J/kg under 50 kOe, respectively. These -ΔS_M~(max) values are comparable to or even higher than that of some reported bulk metallic glasses. Moreover, the larger RC values are due to the broad ΔS_M peak (～200 K), which is caused by the glassy structure. The large ΔS_M and RC values make the Gd-based Gd_(65)Fe_(20)Al_(15-x)B_x glassy ribbons attractive candidates for magnetic refrigeration materials.