Enhanced refrigerant capacity in Gd-Al-Co microwires with a biphase nanocrystalline/amorphous structure

A class of biphase nanocrystalline/amorphous Gd(50+5x)Al(30−5x)Co20 (x = 0, 1, 2) microwires fabricated directly by melt-extraction is reported. High resolution transmission electron microscopy and Fourier function transform based analysis indicate the presence of a volume fraction (∼20%) of ∼10 nm sized nanocrystallities uniformly embedded in an amorphous matrix. The microwires possess excellent magnetocaloric properties, with large values of the isothermal entropy change (−ΔSM ∼ 9.7 J kg−1 K−1), the adiabatic temperature change (ΔTad ∼ 5.2 K), and the refrigerant capacity (RC ∼ 654 J kg−1) for a field change of 5 T. The addition of Gd significantly alters TC while preserving large values of the ΔSM and RC. The nanocrystallites allow for enhanced RC as well as a broader operating temperature span of a magnetic bed for energy-efficient magnetic refrigeration.