Effect of current annealing treatment on magnetic properties of Gd-Al-Co-Fe metallic microfibers

Herein, the influence of annealing current intensities on magnetic properties of Gd-based microfibers was systematically investigated. The experimental results indicated that the as-prepared microfibers have amorphous structure and excellent thermal-stability, and the Curie temperature TC of which slightly change before and after annealing. The general magnetic physical magnitudes (Ms, Mr, μ0Hc and μm) of microfibers increase firstly and then decrease with the rising of annealing current intensities, and those of the microfibers annealed at 90 mA microfibers are more obvious (Ms = 255 A m2/kg and μm = 0.38 ± 0.01). Similarly, the magnetocaloric parameters of microfibers also increase firstly and then decrease with the rising of current intensities. At 5 T of magnetic field change μ0ΔH, the maximum magnetic entropy change ΔSmmax and refrigerant capacity RC of 90 mA annealed metallic microfibers are 12.77 J/(kg·K) and 906 J/kg, respectively, and which remarkably increased in compared with the as-prepared state, respectively. From the microstructural evolution perspective, a certain intensity current annealing induces the tendency of micro-regional clusters and nanocrystals, forming atomic ordered regions, and the internal residual stress release with a reduction of magnetic anisotropy. Meanwhile, the magnetic ordering and the critical magnetic-moment rotational driving-force were changed after Fe-doping, resulting in effective improvement of refrigerant capacity. Accordingly, the current-annealed Gd-Al-Co-Fe microfibers can be adopted as low-temperature magnetic refrigeration working-medium, which also provides a theoretical foundation for magnetic refrigeration technology application.