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Highlights: [•] High-quality Gd55Al25Co20 metallic glass magnetocalorific fibers were melt-extracted. [•] They show superior MCE performance versus its counterpart in BMGs. [•] They have tensile strength of 1189MPa and high security threshold of 796MPa. [•] The excellent performances result from size effect and amorphous structure. [Copyright &y& Elsevier]

High-entropy alloys (HEA) represent potentially disruptive materials across multiple industries, especially for refrigeration technologies. Building metal components layer-by-layer increases design freedom and manufacturing flexibility, thereby enabling high magnetic thermal properties of the multicomponent alloy. However, excessive alloying elements could limit the mass production potential, while prolonging the time to market. Here we demonstrate that a high performance magnetocaloric material can be synthesized from only three elements, HoErFe, by taking advantage of the combination of rare earth and transition elements. Novel medium-entropy alloys (MEA) are prepared by melt-extraction and exhibit excellent magnetocaloric properties. The amorphous/nanocrystalline structure of the microwires, which is confirmed by both transmission electron microscopy (TEM) and X-ray diffraction (XRD), gives the primary contribution to the MCE. The microwires undergo a ferromagnetic-paramagnetic (FM-PM) transition near the Curie temperature (T C = ~44 K), and a spin-glass (SG) behavior could be observed below the T C. The maximum magnetic entropy (-ΔS M max) was 9.5 J kg−1 K−1 under a field change of 5 T. Meanwhile, the refrigerant capacity (RC) and the relative cooling power (RCP) of the alloy microwires were 450 J·kg−1and 588 J kg−1, respectively. The high refrigeration efficiency and high magnetocaloric effect that is reversible make these novel metallic microwires attractive working materials for low-temperature magnetic refrigeration applications. • The novel medium-entropy alloys are prepared by melt-extraction and exhibit excellent magnetocaloric properties. • The wire composite shows a spin-glass behavior below Curie temperature. • The amorphous/nanocrystalline structure of the microwires exhibit enhanced magnetocaloric effect. [ABSTRACT FROM AUTHOR]

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]

Gd-based metallic microfibers have been the research highlights due to the significant magnetocaloric effect. Herein, the atomic cluster micro-regions are constructed in Gd-based microfibers to further improve the magnetocaloric effect. The results show that the continuous and amorphous microfibers with excellent softly magnetic and thermal stability properties are obtained. The maximum magnetic entropy change -Δ S m max of Gd-based microfibers increases first and then decreases with Ni alloying degree increase. Among which, the better magnetocaloric properties is obtained in (Gd 60 A 20 lCo 20) 95 Ni 5 microfibers. The maximum magnetic entropy change, refrigeration capacity (RC), and relative cooling power (RCP) at 5 T reach 11.57 J/kg K, 834.14 J/kg, and 1138.16 J/kg, respectively. The outstanding magnetocaloric properties of microfibers are attributed to the indirect interaction coupling caused by Ni elements and the atomic cluster micro-regions, which lead to a fundamental shift in magnetic entropy. The findings of this study promote the application of Gd-based microfibers in the field of magnetic refrigeration. • The excellent magnetocaloric properties are obtained in GdAlCoNi5 microfibers after Ni alloyed. • The -Δ S m max, RC and RCP of GdAlCoNi5 microfibers reach 11.57 J/kg·K, 834.14 J/kg and 1138.16 J/kg, respectively. • The atomic cluster micro-regions promote the transformation of magnetic entropy disorder to order after Ni alloyed. [ABSTRACT FROM AUTHOR]

In this study, the optimized fabrication and evolution of the microstructure and magnetic transition behavior of the melt-extraction LaFe 11.2 Si 1.8 microwires have been studied. After the optimization of extraction technique (heating power 22 KW, feeding rate 30–50 μm/s, rotation velocity 1700 r/min), the content of La(Fe,Si) 13 phase in the as-extracted microwires was 54 wt% due to the high solidification velocity, which was increased to 85 wt% via annealing at 1373 K for 20 min. The amount of La(Fe,Si) 13 phase was increased and the composition of La(Fe,Si) 13 phase became more homogenized through peritectic reaction and short-distance diffusion in the microwires during annealing process. The coexistence of the nanocrystalline and amorphous structures contributed to the broad magnetic transition temperature range of the as-extracted and annealed microwires. The annealed microwires exhibited a second-order magnetic transformation behavior and showed a maximum magnetic entropy change | ΔS M | max of 6.2 J/kg·K and working temperature interval of 36.0 K under a magnetic field of 20 kOe. Image 1 • LaFe 11.2 Si 1.8 microwires were prepared by melt-extraction technique. • The content of La(Fe,Si) 13 phase in the as-extracted microwire reached 54 wt%. • Nanoscale La(Fe,Si) 13 phase and α-Fe grains were formed in the extracted microwire. • 85 wt% La(Fe,Si) 13 phase was obtained in microwire annealed at 1373 K for 20 min. • The annealed microwire exhibited.| ΔS M | max 6.2 J/kg·K and ΔT FWHM 36.0 K under 20 kOe. [ABSTRACT FROM AUTHOR]

Herein, the magnetocaloric effect (MCE) of Fe-doped Gd-rich microwires has been investigated. Experimental results indicated that this type of the microwires has entirely amorphous microstructure and smooth surface, and exhibits a relatively higher Curie temperature (∼121.8 K) as for the appropriate Fe substitution, and a remarkable and reversible MCE effect with almost no thermal or magnetic hysteresis loss. For a magnetic field change of 5 T, the isothermal magnetic entropy change (-Δ S m ) for the longitudinal direction reaches as large as 10.33 J kg −1 K −1 , besides the refrigerant capacity (RC) achieves a relatively large value of 748.22 J kg −1 . Meanwhile, the Arrott plots also indicate that the ferromagnetic-paramagnetic transition is of the second-order. Therefore, it can be concluded that the obtained Fe-doped Gd-rich wires are used as intelligent materials with enhanced MCE property for potential multifunctional applications in magnetic refrigeration field. [ABSTRACT FROM AUTHOR]

We reported the magnetocaloric properties of Heusler-type Ni 48 Mn 26 Ga 19.5 Fe 6.5 microwires with diameter of ∼50 μm which were fabricated by a precise melt-extraction method. The Fe-doped Ni–Mn–Ga microwires after chemical ordering heat-treatment exhibit negligible thermal and magnetic hysteresis along the axial direction due to their small magnetocrystalline anisotropy and display excellent magnetocaloric effect (MCE) for both magnetic (paramagnetic–ferromagnetic) phase transition and structural (austenite–martensite) phase transition. The maximum entropy change (−Δ S m ), ∼4.7 J kg −1 K −1 , is obtained during the structural transition induced by an external magnetic field of 50 kOe at a temperature of ∼361 K. Moreover, tiny positive magnetic entropy also appears when the applied field is lower than 5 kOe. [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]