Giant berry curvature in amorphous ferromagnet Co2MnGa

Abstract

In amorphous materials, long-range translational order breaks down, and k is no longer a good quantum number; however, some of the phenomena, for instance ferromagnetic interactions and a mechanism similar to the Berry curvature, can be preserved. Here, we demonstrate a giant Berry-curvature-induced anomalous Hall effect and anomalous Hall angle in amorphous Co₂MnGa (a-CMG) thin films. Remarkably, the effect presents the same magnitude as high-quality crystalline CMG with the L2₁ structure. The elastic neutron scattering peak in a-CMG is centered close to the crystalline phase, indicating that the amorphous material presents similar local atomic environments and magnetic interactions. First-principles density functional theory calculations further show that the anomalous Hall conductivity arises only when the local environments in the amorphous structure are similar to the L2₁ phase. Our work strongly points to the application of low-cost, industry-compatible, and thermally stable amorphous topological materials in emerging electronic and spintronic applications.