Unveiling the mechanism of bulk spin-orbit torques within chemically disordered Fe${}_x$Pt${}_{1-x}$ single layers

Abstract

Recent discovery of spin-orbit torques (SOTs) within magnetic single-layers has attracted attention in the field of spintronics. However, it has remained elusive as to how to understand and how to tune the SOTs. Here, utilizing the single layers of chemically disordered Fe${}_x$Pt${}_{1-x}$, we unveil the mechanism of the "unexpected" bulk SOTs by studying their dependence on the introduction of a controlled vertical composition gradient and on temperature. We find that the bulk damping like SOT arises from an imbalanced internal spin current that is transversely polarized and independent of the magnetization orientation. The torque can be strong only in the presence of a vertical composition gradient and the SOT efficiency per electric field is insensitive to temperature but changes sign upon reversal of the orientation of the composition gradient, which are in analogue to behaviors of the strain. From these characteristics we conclude that the imbalanced internal spin current originates from a bulk spin Hall effect and that the associated inversion asymmetry that allows for a non-zero net torque is most likely a strain non-uniformity induced by the composition gradient. The fieldlike SOT is a relatively small bulk effect compared to the dampinglike SOT. This work points to the possibility of developing low-power single-layer SOT devices by strain engineering.

arXiv commentAdvanced Functional Materials (in production)

References in corpus (30)

• Spin torque switching with the giant spin Hall effect of tantalum
• Quantum Spin Hall Effect
• Spin Torque Ferromagnetic Resonance Induced by the Spin Hall Effect
• Spin Transfer Torque Generated by the Topological Insulator Bi_2Se_3
• Interplay of spin-orbit torque and thermoelectric effects in ferromagnet/normal metal bilayers
• Interface control of the magnetic chirality in CoFeB|MgO heterosctructures with heavy metal underlayers
• Tuning the spin Hall effect of Pt from the moderately dirty to the superclean regime
• Single-shot dynamics of spin-orbit torque and spin transfer torque switching in three-terminal magnetic tunnel junctions
• Highly efficient spin current generation by the spin Hall effect in Au${}_{1-x}$Pt${}_x$
• Evolution of the spin Hall effect in Pt nanowires: Size and temperature effects
• Effective spin-mixing conductance of heavy-metal-ferromagnet interfaces
• Ab initio calculation of intrinsic spin Hall effect in semiconductors
• Strong damping-like spin-orbit torque and tunable Dzyaloshinskii-Moriya interaction generated by low-resistivity Pd${}_{1-x}$Pt${}_x$ alloys
• Planar Hall torque
• On the origin of field-like spin-orbit torques in heavy metal-ferromagnet-oxide thin film heterostructures
• Electrical switching of perpendicular magnetization in L10 FePt single layer
• Perspectives of Electrically generated spin currents in ferromagnetic materials
• The spin Hall effect of Bi-Sb alloys driven by thermally excited Dirac-like electrons
• Reorientable Spin Direction for Spin Current Produced by the Anomalous Hall Effect
• Current-induced magnetization switching in CoTb amorphous single layer
• Current-induced spin torques on single GdFeCo magnetic layers
• Electric-field control of spin-orbit torques in perpendicularly magnetized W/CoFeB/MgO films
• Observation of strong bulk damping-like spin-orbit torque in chemically disordered ferromagnetic single layers
• Strong enhancement of the spin Hall effect by spin fluctuations near the Curie point of FexPt1-x alloys
• Energy-efficient ultrafast SOT-MRAMs based on low-resistivity spin Hall metal Au0.25Pt0.75
• Giant spin Hall Effect in two-dimensional monochalcogenides
• Strain-engineering of the charge and spin-orbital interactions in Sr2IrO4
• Planar Hall driven torque in a FM/NM/FM system
• Strain-induced nonlinear spin Hall effect in topological Dirac semimetal
• Large spin-Hall effect in Si at room temperature

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• Giant bulk spin-orbit torque and efficient electrical switching in single ferrimagnetic FeTb layers with strong perpendicular magnetic anisotropy
• From Early Theories of Dzyaloshinskii-Moriya Interactions in Metallic Systems to Today's Novel Roads
• Current-induced perpendicular effective magnetic field in magnetic heterostructures
• Gigantic Anisotropy of Self-Induced Spin-Orbit Torque in Weyl Ferromagnet Co2MnGa
• Boosting spin-orbit torque efficiency in spin-current generator/magnet/oxide superlattices
• Anomalous sign inversion of spin-orbit torque in ferromagnetic/nonmagnetic bilayer systems due to self-induced spin-orbit torque
• Vertically Graded Fe-Ni Alloys with Low Damping and a Sizeable Spin-Orbit Torque
• Self-induced spin pumping and inverse spin Hall effect in single FePt thin films
• Negligible current-induced torque from the bulk and interface of Al