Abstract
Electrical control of magnetization is of crucial importance for integrated spintronics devices. Spin-orbit torques (SOT) in heavy-metal/ferromagnetic heterostructures have emerged as a promising tool to achieve efficiently current-induced magnetization reversal. However, the microscopic origin of the SOT is being debated, with the spin Hall effect (SHE) due to nonlocal spin currents and the spin Rashba-Edelstein effect (SREE) due to local spin polarization at the interface being the primary candidates. We investigate the electrically induced out-of-equilibrium spin and orbital polarizations in pure Pt films and in Pt/$3d$-metal (Co, Ni, Cu) bilayer films using ab initio electronic structure methods and linear-response theory. We compute atom-resolved response quantities that allow us to identify the induced spin-polarization contributions that lead to fieldlike (FL) SOTs, mostly associated with the SREE, and dampinglike (DL) SOTs, mostly associated with the SHE, and compare their relative magnitude, dependence on the magnetization direction, as well as their Pt-layer thickness dependence. We find that both the FL and DL components contribute to the resulting SOT at the Pt/Co and Pt/Ni interfaces, with the former contributions being larger at the Pt interface layer and the latter larger in the Co or Ni layers. Our calculations show that the electrically induced transverse orbital polarization is exceedingly larger than the induced spin polarization and present even without spin-orbit coupling, in contrast to the spin polarization.
Highlights
Electrical control of magnetization has attracted considerable attention because of its potential for high-speed spin-based memories with low-power consumption
Following theoretical predictions [1,2] it was shown that the magnetization of a ferromagnetic layer in a multilayer stack can be switched with a spin-transfer torque (STT) exerted by a spin-polarized electric current flowing through the magnetic layer in perpendicular direction [3,4,5,6,7]
We artificially introduce a spin-orbit coupling (SOC) scaling parameter α in the density functional theory (DFT) calculations such that H0 can be written as H0 = Hsc + αHsoc where Hsc is the scalar-relativistic part of the Hamiltonian and Hsoc the SOC part
Summary
Electrical control of magnetization has attracted considerable attention because of its potential for high-speed spin-based memories with low-power consumption. Following theoretical predictions [1,2] it was shown that the magnetization of a ferromagnetic layer in a multilayer stack can be switched with a spin-transfer torque (STT) exerted by a spin-polarized electric current flowing through the magnetic layer in perpendicular direction [3,4,5,6,7]. SOT can be observed in a heavy-metal/ferromagnetic bilayer film where the current flows dominantly through the heavy metal and parallel to the ferromagnetic layer.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
