Probing the Spin Hall Characteristics of W/CoFeB/MgO Based Heterostructures for Spin‐Orbit Torque Based Magnetic Random Access Memory Application

Abstract

In this work, the spin Hall characteristics of W/CoFeB/MgO have been systematically studied to provide an in‐depth insight for the optimization of the SOT‐MRAM channel. The bcc and β phases of tungsten (W) are identified clearly from XRD and resistivity studies, which shows marked impact on the electrical characteristics. Moreover, the same is found have tremendous affect on W's spin Hall characteristics with a twelvefold increase of the spin Hall angle ΘSH. The evaluation of W/CoFeB interfacial spin mixing conductance geff↑↓ using ab initio studies shows good coherency with the same evaluated experimentally, which is used to estimate interfacial spin transparency T</> to accurately evaluate intrinsic spin Hall conductivity σSH of W. The findings equivocate for a strong claim on β‐W's σSH to be around −0.23 ∓ 0.03, addressing the ongoing discrepancy. Increasing boron concentration in (Co1Fe3)100−xBx and thermal annealing temperature are found to reduce ΘSH effectively which is inferred to boron diffusion toward W. Alloying of W with Ta does not necessarily enhance ΘSH, for which very optimized relative concentration and the alloy growth phase is critical. The findings can significantly contribute to the ongoing SOT‐MRAM development for achieving various means of control for improvement in the device characteristics.

Magneto‐Ionics in Annealed W/CoFeB/HfO2 Thin Films

“…It is therefore of importance to characterize magneto-ionics in annealed CoFeB systems to optimize both the magnetic properties of the films and their magnetoionic performance. W/CoFeB-based systems are known to exhibit DMI and PMA, as well as a large spin Hall angle in the β-phase of W, [18][19][20] which makes them very attractive for spintronics applications. In these systems, post-growth annealing is systematically used to enhance DMI, and PMA, [18] which in W/CoFeB/MgO is associated with the crystallization of CoFeB.…”

Large Field-like Spin–Orbit Torque and Enhanced Magnetization Switching Efficiency Utilizing Amorphous Mo

“…Over the past decade, spin–orbit torque (SOT) − has emerged as a promising alternative to spin-transfer torque (STT) and has been intensively investigated. In particular, the SOT-driven switching of ferromagnets (FMs) with perpendicular magnetic anisotropy (PMA) has attracted extensive attention because of its potential for lower-power and faster magnetization manipulations. − , Among various magnetic heterostructures that give rise to PMA, heavy metals (HMs)/CoFeB/MgO becomes standard heterostructures for SOT study ,− because of their compatibility in magnetic tunnel junctions (MTJs) with high tunneling magnetoresistance (TMR). , Usually, HMs with large spin–orbit coupling (SOC) , are the most explored as efficient generators of spin current to produce SOTs, such as Pt, Ir, Ta, W, and some transition metal dichalcogenides . Mo is another 4d transition HM, albeit with a predicted weaker SOC, but it still plays a vital role in the construction of CoFeB/MgO-based perpendicular MTJs (p-MTJs). , …”