Electrical, magnetic, and Hall properties of AlxCoCrFeNi high-entropy alloys

This investigation explores the electrical and magnetic properties of as-cast, -homogenized, and -deformed AlxCoCrFeNi (C-x, H-x, and D-x, respectively) alloys at various temperatures from 4.2 to 300 K. Experimental results reveal that carrier density of the alloys is of 1022–23 cm−3. H-x has a carrier mobility of 0.40–2.61 cm2 V−1 s−1. The residual electrical resistivity of the alloys varies from 100 to 220 μΩ cm. The temperature coefficient of resistivity (TCR) of H-2.00 is small (82.5 ppm/K). Therefore, defects in the lattice dominate electrical transportation. Some compositions exhibit Kondo-like behavior. At 300 K, H-0.50, H-1.25, and H-2.00 are ferromagnetic, while H-0.00, H-0.25, and H-0.75 are paramagnetic. Al and AlNi-rich phases reduce the ferromagnetism of single FCC and single BCC H-x, respectively. Spin glass behavior of some compositions is also observed. Alloys H-x are of the hole-like carrier type, and ferromagnetic H-x exhibits an anomalous Hall effect (AHE).

Research highlights▶ Values of ρ0 at4.2 K for multi-principal-element alloys C-x, H-x, and D-x are 111.06–196.49, 93.78–162.77, and 120.48–162.05 μΩ cm, respectively. With the same level of carrier density, they are larger than those of conventional alloys, but smaller than those of amorphous ones. RRR values range from 1.03 to 1.27. That is, the electronic transportation in the studied alloy system is dominated by the defects of lattice. These facts imply that the degree of defects in a single lattice for these high-entropy alloys is lower than for amorphous ones, but larger than conventional ones. The TCR value of H-2.00 listed is small (82.5 ppm/K). From the ρ0(T) fitting, it is demonstrated that the Kondo-like behavior exists for some compositions. ▶ BCC phase has high Ms value at low temperature in this alloy system. At 300 K, alloys H-0.50, H-1.25, and H-2.00 are ferromagnetic, while alloys H-0.00, H-0.25, and H-0.75 are paramagnetic. Al and AlNi-rich phases decreases ferromagnetism for single FCC and single BCC alloys H-x, respectively. The spin glass behavior is observed for some compositions of this study. ▶ Alloys H-x are of the hole-like carrier type. The stronger the ferromagnetic alloys the higher the %AHE, i.e., the anomalous Hall effect (AHE) is magnetic dependent. Carrier density for H-x (1022–23 cm−3) is similar to that for conventional alloys. Alloys H-x have small carrier mobility (0.40–2.61 cm2 V−1 s−1). It is associated with the heavier lattice defects of HEAs as compared to the conventional alloys with the same carrier density.