Large Anomalous Hall Effect in a Nanocrystalline Room-Temperature Ferromagnetic CoCrFeNiGa High-Entropy Alloy

Magnetic high-entropy alloys (HEAs) with their unusual blend of long-range magnetic order and exceptional mechanical properties are beneficial for the development of next-generation spintronic devices that can withstand extreme conditions. Developing room-temperature magnetic HEAs and understanding the link among their magnetic, electronic, and mechanical properties are crucial. Here, we introduce nanocrystalline CoCrFeNiGa as a room-temperature bulk magnetic HEA candidate based on 3d-transition metals and elucidate its magnetic and electronic properties. Structural characterization reveals the existence of mixed BCC and FCC phases with a crystallite size of ∼51 nm. CoCrFeNiGa shows a high Curie temperature (T_C) of ∼872 K and soft magnetic behavior with minimal coercivity. We also observed spin freezing below 60 K, likely due to competing magnetic interactions among its 3d-transition metals. Electrical resistivity measurements confirm metallic behavior with magnon contributions below 50 K. Interestingly, CoCrFeNiGa exhibits a large anomalous Hall effect (AHE), with an anomalous Hall conductivity of ∼603 S·cm^-1 at 5 K and ∼144 S·cm^-1 at 300 K, persisting despite inherent disorder. This AHE is primarily attributed to an intrinsic mechanism. The combination of the above room-temperature magnetic order, soft magnetic properties, a large intrinsic AHE, and competing magnetic interactions positions CoCrFeNiGa as a prospective candidate for the development of next-generation robust spintronic devices and architectures using nanocrystalline magnetic HEAs, which are resilient under demanding conditions.