Influence of intermixing at the Ta/CoFeB interface on spin Hall angle in Ta/CoFeB/MgO heterostructures

Abstract

When a current is passed through a non-magnetic metal with strong spin-orbit coupling, an orthogonal spin current is generated. This spin current can be used to switch the magnetization of an adjacent ferromagnetic layer or drive its magnetization into continuous precession. The interface, which is not necessarily sharp, and the crystallographic structure of the nonmagnetic metal can both affect the strength of current-induced spin-orbit torques. Here, we investigate the effects of interface intermixing and film microstructure on spin-orbit torques in perpendicularly magnetized Ta/Co40Fe40B20/MgO trilayers with different Ta layer thickness (5 nm, 10 nm, 15 nm), greater than the spin diffusion length. Effective spin-orbit torques are determined from harmonic Hall voltage measurements performed at temperatures ranging from 20 K to 300 K. We account for the temperature dependence of damping-like and field-like torques by including an additional contribution from the Ta/CoFeB interface in the spin diffusion model. Using this approach, the temperature variations of the spin Hall angle in the Ta underlayer and at the Ta/CoFeB interface are determined separately. Our results indicate an almost temperature-independent spin Hall angle of in Ta and a strongly temperature-dependent for the intermixed Ta/CoFeB interface.

CoFeB/MgO/CoFeB structures with orthogonal easy axes: perpendicular anisotropy and damping

“…While the magnetic parameters practically do not depend on the MgO thickness in as-deposited structures, the annealed structures show a substantial spread in 4πM ef f as it is shown in Fig. 6, which may imply some different CoFeB/MgO interfaces due to, for example, boron diffusion [30,33].…”

Temperature study of the giant spin Hall effect in the bulk limit of β−W

“…In reality, the interfacial transparency is less than unity. The loss in transmission is partly due to the spin backflow at the abrupt interface, and partly caused by the enhanced spin scattering from the interfacial region [15,25,34,35]. A semi-classical driftdiffusion formalism has been developed to calculate the spin transmission probability P tran for the β-W/Ferromagnet (FM) bilayer system [15,21,24,25],…”

The influence of an ultra-high resistivity Ta underlayer on perpendicular magnetic anisotropy in Ta/Pt/Co/Pt heterostructures

“…[19][20][21][22][23][24] The same results were also reported for high resistivity b-Ta based multilayered lm structures. [25][26][27][28] Moreover, the insertion of a non-magnetic layer between the heavy metal/magnetic metal layers will also affect the spin-orbit coupling (SOC) of the lm interface, and an appropriate insertion layer can effectively improve the PMA and reduce the spin Hall current density. [29][30][31][32] However, there are few studies on the inuence of the inserted heavy metal layer non-adjacent to the magnetic metals on PMA and SOT in the heavy metal/magnetic metal multi-layered lms.…”