Strong transverse spin current generation in bulk ferromagnetic materials*

The intrinsic spin Hall effect (SHE) is widely studied in non-magnetic metals and semiconductors. Recent studies have reported the observation of an inverse SHE (ISHE) in 3d ferromagnetic alloys where the underlying spin currents that generate the ISHE are oriented along the magnetization direction of permalloy (Py) [1]. Subsequent studies report a non-trivial SHE in Py [2,3] where the spin-polarization is not oriented along the magnetization; its origin in a 3d magnetic alloy is not known. To shed some light on the intrinsic SHE in magnetic materials we calculate transverse spin currents as a function of concentration x for fcc Fe_xNi_1-x alloys within a first-principles DFT-LDA scattering framework. For Py we find a spin Hall angle (SHA) of 4.8% compared to a value of 5% we calculate for platinum at room temperature [4]. We find a surprisingly large transverse spin current that is polarized along the same direction that could be useful in field-free switching applications.