Giant spin Hall effect in perpendicularly spin-polarized FePt/Au devices

Abstract

Conversion of charge current into pure spin current and vice versa in non-magnetic semiconductors or metals, which are called the direct and inverse spin Hall effects (SHEs), provide a new functionality of materials for future spin-electronic architectures. Thus, the realization of a large SHE in a device with a simple and practical geometry is a crucial issue for its applications. Here, we present a multi-terminal device with a Au Hall cross and an FePt perpendicular spin injector to detect giant direct and inverse SHEs at room temperature. Perpendicularly magnetized FePt injects or detects perpendicularly polarized spin current without magnetic field, enabling the unambiguous identification of SHEs. The unprecedentedly large spin Hall resistance of up to 2.9 mOmega is attributed to the large spin Hall angle in Au through the skew scattering mechanism and the highly efficient spin injection due to the well-matched spin resistances of the chosen materials.

Giant spin Hall effect in graphene grown by chemical vapour deposition

“…The large enhancement in SOC allows the generation of spin currents via the spin Hall effect (SHE) 23,24 with an exceptionally large spin Hall coefficient (angle) gB0.2. The latter is comparable to what has been observed in gold (Au) 25 , platinum (Pt) 26 or tungsten (W) 3 thin films with thickness at least 10 times larger than that of graphene. Here, what differentiates graphene is the strong Fermi-energy dependence of the density of states and its sharp sensitiveness to adsorbed species making it a test bed for extrinsically generated SHE 8 .…”

“…Finally, we discuss how metallic adatoms lead to a robust SHE with such a large g. A large g in pure metals such as Pt (0.01 À 0.1) has been ascribed to resonant scattering on impurity states split by the spin-orbit interaction 25,43 . The importance of such resonant scatterers in graphene is also well established 8,44 .…”

Spin caloritronics

“…Seki et al [34] found experimental evidence for a thermal Hall effect in Au|FePt structures, which can be due either to an anomalous Nernst effect in FePt or a spin Nernst effect in Au. In GaMnAs the planar [35] and anomalous [36] Nernst effects have been observed, with intriguing temperature dependences.…”

Spin-charge coupled dynamics driven by a time-dependent magnetization

“…The inverse spin Hall voltage is associated with the spin Hall angle θ sH , which is defined as the ratio of the spin Hall and charge conductivities. Large spin Hall angles are typically found in transition metals such as Au [9,11], Pt [7,9,[12][13][14], and Ta [14,15]. The same class of setups is also used to study the reciprocal effect, when spin currents generated in the normal layer enter the magnetic material and exert a torque on its magnetization [13,[15][16][17].…”