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The microstructure and magnetic properties including magnetocaloric performance of as-prepared and heat-treated La(Fe,Ni) 11.5 Si 1.5 alloys were systematically investigated. The experimental results indicate that the as-prepared La(Fe,Ni) 11.5 Si 1.5 alloys are composed of α-Fe phase and LaFeSi phase, and the saturation magnetization M s can achieve 159.1 emu/g, as for the larger content of ferromagnetic α-Fe phase. The peritectic reaction occurs during vacuum annealing process, and the decrease of α-Fe phase content reduced the hysteresis loss, meanwhile the NaZn 13 -type structure (1:13 phase) generated. In particular, the magnetocaloric properties of La(Fe,Ni) 11.5 Si 1.5 alloys annealed at 1373 K are superior to that of annealed at 1323 K. And the magnetic entropy change (-Δ S m) of the alloys annealed at 1373 K is up to 20.87 J kg−1 K−1, while Refrigeration Capacity (RC) reaches 415.59 J kg−1 at a magnetic field of 5 T. From the perspective of solid-phase reaction dynamics, the increase of annealing temperature could beneficially accelerate the peritectic reaction process, and result in the increasing content of 1:13 phase, thereby enhancing their magnetocaloric characteristics. Therefore, the microstructure and magnetocaloric properties of La(Fe,Ni) 11.5 Si 1.5 alloys could be effectively modulated by optimizing the annealing process, and it also provides a significant technical reference for the practical application of room-temperature Magnetic Refrigeration (MR) technology. Magnetocaloric properties of La(Fe,Ni) 11.5 Si 1.5 alloys based on NaZn 13 -type structure are distinctly enhanced by modulation of vacuum annealing treatment and Ni-doping. Image 1 • Effects of impurity phases on the magnetic properties were studied in detail. • The saturation magnetization and hysteresis loss of as-prepared alloy are larger than them of heat-treated alloy. • The formation of La(Fe,Ni,Si) 13 (1:13) phase in the alloy is promoted by annealed at higher temperature. • Magnetocaloric properties of La(Fe,Ni) 11.5 Si 1.5 alloy can be effectively improved by rising annealing temperature. [ABSTRACT FROM AUTHOR]

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 T C of which slightly change before and after annealing. The general magnetic physical magnitudes (M s , M r , μ 0 H c and μ m) 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 (M s = 255 A m2/kg and μ m = 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 μ 0 Δ H , the maximum magnetic entropy change Δ S m max 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. Magnetocaloric properties of Gd-Al-Co-Fe metallic microfibers current-annealed at 90 mA are significantly improved according to the microstructural evolution and magnetic ordering modulation. Image 1 • Effects of current annealing intensities on the magnetic properties were investigated in detail. • MCE characteristics of Gd-Al-Co-Fe microfibers could be obviously improved at 90 mA. • Magnetocaloric mechanism is illustrated by the perspective of structural evolution and magnetic ordering transformation. [ABSTRACT FROM AUTHOR]