Giant berry curvature in amorphous ferromagnet Co2MnGa

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.