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

Abstract

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 505K (for x=0.5) to 526K (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 0.62–1.25Jkg−1K−1 and 62–158.75Jkg−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 2T. 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 1T, 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 400–600K.