Improving magnetocaloric properties of Fe_68–xCr_xTb₅B₂₃Nb₄ (x = 0, 2, 4, 6 and 8) metallic glasses having high glass-forming ability with tunable Curie temperature

Abstract

The impacts of adding Cr on the Curie temperature (T_C), glass-forming ability (GFA), and magnetocaloric effect were studied in Fe_68−xCr_xTb₅B₂₃Nb₄ (x = 0, 2, 4, 6 and 8) metallic glasses prepared by suction casting. GFA depends on Cr content in the composition. For Fe_68−xCr_xTb₅B₂₃Nb₄ bulk metallic glasses (BMGs), with critical diameters up to ~3 mm can be produced by suction casting and maximum value of GFA was found for x = 6. By exchanging Cr with Fe partially, T_C could effectively be adjusted in a quite broad temperature interval from 487 K for x = 0 to 267 K for x = 8, whereas maximum magnetic entropy change decreased from 1.16 to 0.53 Jkg⁻¹ K⁻¹ and refrigeration capacity (RC) changed from 116 to 45.05 J/kg under a low field change of 2 T. Though T_C is shifted to room temperature, maximum magnetic entropy change and RC decreased almost half of the base alloy. To enhance these properties (Fe_0.62Cr_0.06Tb_0.05B_0.23Nb_0.04)_100−yCu_y (y = 0.75, 1), metallic glasses are prepared. By the help of small addition of Cu, magnetocaloric properties can be effectively increased without changing the T_C. These findings show that the successful synthesis of the Fe-based Fe₆₂Cr₆Tb₅B₂₃Nb₄ and (Fe_0.62Cr_0.06Tb_0.05B_0.23Nb_0.04)_100−yCu_y (y = 0.75, 1) BMGs near room temperature, could be considered as promising candidates as magnetic refrigerant materials.

Keywords:

• Metallic glasses
• magnetocaloric effect
• magnetic entropy change