Effect of Gd Substitution on the Structural, Magnetic, and Magnetocaloric Properties of Fe68Tb₅B23Nb₄ Metallic Glass

Abstract

The effects of adding Gd on the Curie temperature (TC), glass-forming ability (GFA), and magnetocaloric effect (MCE) were studied in FeSUB68-x/SUBGdSUBx/SUBTb₅BSUB23/SUBNb₄ (x = 0, 2, and 6) glassy alloys prepared by suction casting. It was shown that when Gd content was exchanged with Fe partially for x = 2, GFA was increased, whereas for x = 6, adding Gd content has reduced the GFA and amorphous structure could not be obtained. Critical diameter was found to be 3 ㎜ for FeSUB66/SUBGd₂Tb₅BSUB23/SUBNb₄ bulk metallic glass (BMG). By exchanging Gd with Fe partially, TC could effectively be tuned in a quite broad temperature interval from 487 K (x = 0) to 380 K (x = 6) for which amorphous structure could not be obtained. Maximum magnetic entropy change (−ΔSSUBM/SUB)SUPmax/SUP values were found to be 1.16, 0.84 JkgSUP−1/SUPKSUP−1/SUP, and 0.54 J㎏SUP−1/SUPKSUP−1/SUP as well as, refrigeration capacity (RC) values were obtained as 116 J/㎏, 84.84 J/㎏, and 40.50 J/㎏ under a low field change of 2 T for x = 0, 2, and 6, respectively. Although TSUBC/SUB was shifted to lower temperatures by exchanging Fe with Gd partially, −(ΔSSUBM/SUB)SUPmax/SUP decreased almost half of the base alloy and RC decreased approximately 1/3 of the base alloy.