Magnetocaloric effect and temperature-dependent magnetoresistance in Cu-doped FeCoNiBSiNb amorphous alloys

In this work, magnetocaloric and magnetoresistance properties of Fe-based (Fe0.402Co0.201Ni0.067B0.227Si0.053Nb0.05)100 - xCux (x = 0, 0.5, 0.75, 1) amorphous ribbons formed by melt-spinning method and the effect of Cu on these properties were investigated. Curie temperature (TC) was not changed with the addition of Cu up to 0.5% to the composition. On the other hand, for Fe-based (Fe0.402Co0.201Ni0.067B0.227Si0.053Nb0.05)100−xCux (x = 0.75 and 1), TC increased from 505 K (for x = 0.5) to 526 K (for x = 0.75) and almost remain constant for x = 1. Maximum magnetic entropy change (−ΔSM)max and refrigeration capacity (RC) values were found to be in the range of 0.62-1.25 Jkg− 1K− 1 and 62-158.75 Jkg− 1 respectively for (Fe0.402Co0.201Ni0.067B0.227Si0.053Nb0.05)100 − xCux (x = 0, 0.5, 0.75, 1) amorphous ribbons under a maximum field of 2 T. These values are comparable with those of previously studied Fe-based metallic glasses. In addition, the maximum temperature dependent magnetoresistance (MR (%)) values for (Fe0.402Co0.201Ni0.067B0.227Si0.053Nb0.05)100 − xCux (x = 0, 0.5, 0.75, 1) were found to be 125, 17, 7, and 1% around the Curie temperatures under an applied field of 1 T, respectively. The magnetoresistance values of Cu-free Fe-based glassy alloy are higher than those of Cu-doped alloys. The results show that appropriate amount of Cu substitution (x = 0.75, 1) can enhance the RC and (−ΔSM)max. The suitable RC, large magnetoresistance, good thermal stability, and negligible hysteresis offer that these Fe-based glassy alloys exhibit promising applications as high-temperature magnetic refrigerants and multi-functional materials working in the temperature range of 400-600 K.