First-Principles Study on Spin Hall Conductivity of Transition Metals and Their Alloys
Do Duc Cuong
Department of Physics and Computer Science, Faculty of Physics and Engineering Physics, University of Science, VNU-HCM, Vietnam
Abstract
Spintronics has rapidly emerged as a highly pursued research area in solid-state physics and devices owing to its potential application in low power memory and logic as well as the rich physics associated with it. Traditionally in spintronics, Giant Magneto Resistance (GMR) in spin valves and Tunnel Magneto Resistance (TMR) effects in magnetic tunnel junctions have been used to manipulate ferromagnets. Even large achievement has been obtained in spintronics using GMR and TMR, switching magnetization is still based on the external magnetic field, which requires a large current. Recently, current-induced magnetization switching has been extensively studied due to its advantages over the methods using the external magnetic field. Two concepts using current-induced magnetization switching have been proposed: spin-transfer torque (STT) and spin-orbit torque (SOT), where SOT is found to provide lower power consumption, faster switching, and more stability compared to STT method. However, to realize SOT devices, a large spin current is always required. Therefore, finding the materials which can create a large spin current has become the big challenge.
Spin Hall effect (SHE) is the common method used to generate the spin current. Non-magnetic heavy transition metals (TMs) are expected to give large spin Hall conductivity (SHC) for their large spin-orbit coupling. Among transition metals, b-W, in A15 structure, has been reported to have large SHC [1-3], and alloys of b-W are expected to have even higher SHC [2]. In this work, we present first principles study of b-W alloying with V and Ta for their SHCs. For each alloy composition, possible configurations are investigated, whose relative energetics are used for thermodynamic average of SHCs. While similar band structures are expected for both alloys, considering the same valence electrons of Ta and V, the resulting SHCs exhibit different behavior. More specifically, SHC of the V-W alloy reaches up to -1208 ℏ/e
S/cm, which is about 48% larger than -817 ℏ/e S/cm of b-W, when concentration of V is 25%, while that of Ta-W alloy decreases with Ta concentration.
References
[1] K. Demasius et al., Nat. Commun. 7, 10644 (2016).
[2] X. Sui et al., Phys. Rev. B 96, 241105(R) (2017).
[3] E. Derunova et al., Sci. Adv. 5, eaav8575 (2019).