Spin-fluctuation induced enhancement for pure spin current

In this work, we study the interplay of pure spin current and spin fluctuation in ferromagnetic NiCu alloys. By tuning the compositions of the alloys, we shift the Curie temperature in a wide range. We demonstrate a significantly enhanced spin current through spin fluctuation at the Curie temperature. Most importantly, in the specific composition of Ni 0.8 Cu 0.2 , we obtain an unprecedentedly large spin Hall angle of 46%, about 5 times larger than that of Pt at room temperature. The 3d magnetic alloys function as higly efficient spin Hall materials.