Enhanced refrigerant capacity and Curie temperature of amorphous Gd60Fe20Al20 microwires

Gd60Fe20Al20 microwires with an average diameter of similar to 44 mu m were fabricated by the melt-extraction method. XRD, TEM and HRTEM confirmed the amorphous nature of the microwires. The dimensional and chemical uniformity of the microwires over their length were confirmed by SEM and EDS, respectively. Magnetization measurements revealed a broad paramagnetic to ferromagnetic phase transition at T-C similar to 202 K. For mu(0)Delta H = 5 T, the microwires exhibit a broad magnetic entropy change with its maximum value Delta S-M(max) of similar to 4.8 J kg(-1) K-1 and a large refrigerant capacity (RC) of similar to 687 J kg(-1) over a large temperature interval (150 K). This RC value of the microwires is larger than those of the previously reported bulk and ribbon counterparts. An analysis of critical exponents reveals that gamma = 1.246 +/- 0.017 is close to that predicted by the 3D Ising theoretical model, while beta = 0.723 +/- 0.011 does not agree with any of the critical exponents predicted by the existing models. This can be attributed to the antiferromagnetic coupling between the rare earth (Gd) and the transition metal (Fe). The origins of the broad magnetic phase transition, the broad magnetic entropy change, and the large refrigerant capacity are discussed. (C) 2019 Elsevier B.V. All rights reserved.