Efficient generation of spin-orbit torques is central for the exciting field of spin-orbitronics. Platinum, the archetypal spin Hall material, has the potential to be an outstanding provider for spin-orbit torques due to its giant spin Hall conductivity, low resistivity, high stabilities, and the ability to be compatible with CMOS circuits. However, pure clean-limit Pt with low resistivity still provides a low damping-like spin-orbit torque efficiency, which limits its practical applications.

The recent discovery of spin-orbit torques (SOTs) within magnetic single-layers has attracted attention. However, it remains elusive as to how to understand and how to tune the SOTs. Here, utilizing the single layers of chemically disordered FexPt1-x, the mechanism of the “unexpected†bulk SOTs is unveiled by studying their dependence on the introduction of a controlled vertical composition gradient and temperature. The bulk dampinglike SOT is found to arise from an imbalanced internal spin current that is transversely polarized and independent of the magnetization orientation.

Using a multilayer containing a cobalt detector layer, a copper spacer, and a Permalloy source layer, we show experimentally how the nonreorientable spin-orbit torque generated by the Permalloy source layer - the component of spin-orbit torque that does not change when the Permalloy magnetization is rotated - can be measured using spin-torque ferromagnetic resonance (ST FMR) with line-shape analysis.

In-plane current-induced strong dampinglike spin-orbit torque (SOT) can enable sub-nanosecond switching of thin-film nanomagnets for nonvolatile magnetic storage [1]. Enormous efforts have been made on developing energy-efficient, high-endurance, integration-friendly spin current generators (SCGs) [2], [3] that can provide high dampinglike SOT efficiency (xi DL j).

When spin-orbit torques are measured using spin-torque ferromagnetic resonance, two alternative ways of analyzing the results to extract the torque efficiencies - lineshape analysis and analysis of the change in linewidth versus direct current - often give inconsistent results. We identify a source for these inconsistencies.

We present measurements of spin-orbit torques generated by Ir as a function of film thickness in sputtered Ir/CoFeB and Ir/Co samples. We find that Ir provides a dampinglike component of spin-orbit torque with a maximum spin-torque conductivity σDLeff=(1.4±0.1)×105-2eω-1m-1 and a maximum spin-torque efficiency of ζDL=0.042±0.005, which is sufficient to drive switching in a 0.8 nm film of CoFeB with perpendicular magnetic anisotropy. We also observe a surprisingly large fieldlike spin-orbit torque (FLT).

Spin-orbit torque can drive electrical switching of magnetic layers. Here, we report that, at least for micrometer-sized samples, there is no simple correlation between the efficiency of dampinglike spin-orbit torque (ζDLj) and the critical switching current density of perpendicularly magnetized spin-current generator-ferromagnet heterostructures.

Emergent quantum phenomena in electronically coupled two-dimensional heterostructures are central to next-generation optical, electronic, and quantum information applications. Tailoring electronic band gaps in coupled heterostructures would permit control of such phenomena and is the subject of significant research interest. Two-dimensional polymers (2DPs) offer a compelling route to tailored band structures through the selection of molecular constituents.

A diverse set of SOT materials with vastly different values of spin efficiency, conductivity, and thickness are being explored to achieve the lowest write energy. Research on SOT-assisted STT-MRAM and novel materials for the switching of magnets with perpendicular magnetic anisotropy (PMA) is also ongoing. This paper presents a comprehensive study on the impact of material parameters on array-level read and write operations for both in-plane and PMA MRAM cells. The results offer important guidelines for material development for this technology. © 2020 IEEE.