Resolving Discrepancies in Spin-Torque Ferromagnetic Resonance Measurements: Lineshape versus Linewidth Analyses

Karimeddiny, Saba; Ralph, Daniel

doi:10.1103/physrevapplied.15.064017

Cited by 9 publications

(8 citation statements)

References 22 publications

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“…The precession of M further causes the oscillation of device resistance through the anisotropic magnetoresistance of CoFeB, which is detected as the mixing ST-FMR voltage V by a lock-in amplifier. Figure 4c-e shows the FMR spectra in Co(Ni, Fe)Si/Cu/CoFeB heterostructures with ϕ = 45° and the frequency f = 8 GHz, in which the contributions of symmetric (V S ) and antisymmetric (V A ) Lorentzian line shapes are separated from the V by [35,36] ( ) where the Δ is the resonance linewidth, H res represents the resonance field, and C is the constant voltage offset. The contribution of V S in the total FMR signals is known to be caused by the damping-like SOT, while the V A part is from the Oersted field and field-like torque.…”

Section: Resultsmentioning

confidence: 99%

“…The precession of M further causes the oscillation of device resistance through the anisotropic magnetoresistance of CoFeB, which is detected as the mixing ST‐FMR voltage V by a lock‐in amplifier. Figure 4c–e shows the FMR spectra in Co(Ni, Fe)Si/Cu/CoFeB heterostructures with φ = 45° and the frequency f = 8 GHz, in which the contributions of symmetric ( V S ) and antisymmetric ( V A ) Lorentzian line shapes are separated from the V by [ 35,36 ]

\begin{array}{*{20}{c}}{V = {V_{\rm{S}}}\frac{{{\Delta ^2}}}{{{{\left( {H - {H_{{\rm{res}}}}} \right)}^2} + {\Delta ^2}}} + {V_{\rm{A}}}\frac{{\Delta \left( {H - {H_{{\rm{res}}}}} \right)}}{{{{\left( {H - {H_{{\rm{res}}}}} \right)}^2} + {\Delta ^2}}} + C}\end{array}

where the Δ is the resonance linewidth, H res represents the resonance field, and C is the constant voltage offset. The contribution of V S in the total FMR signals is known to be caused by the damping‐like SOT, while the V A part is from the Oersted field and field‐like torque.…”

Section: Resultsmentioning

confidence: 99%

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Elemental Doping and Interface Effects on Spin–Orbit Torques in CoSi‐Based Topological Semimetal Thin Films

Wen

Seki

et al. 2022

Adv Materials Inter

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This work reports on Ni and Fe doping and interface effects on spin–orbit torques (SOTs) generated from a topological semimetal CoSi. CoSi thin films grown on Al2O3(0001) substrates by magnetron co‐sputtering show the B20 structure with a texture in the [210] orientation even after Ni or Fe doping. The SOTs from the films exerted on the magnetization of a CoFeB layer are evaluated by harmonic Hall and spin‐torque ferromagnetic resonance measurements. The spin Hall efficiency ξSH of the textured B20‐CoSi at room temperature is determined to be 9.6%, which decreases to 1.8% for Ni0.15Co0.85Si and to 5.5% for Fe0.26Co0.74Si. The electrical conductivity dependence of the spin Hall conductivity is assigned to the regime of intrinsic mechanism of spin Hall effect, suggesting that the reduction of ξSH with the element doping can be due to the degradation in topological electronic structures of CoSi. Furthermore, inserting a Cu layer at the Co(Ni, Fe)Si/CoFeB interface results in an increase of the ξSH up to 10.9% for CoSi, 4.0% for Ni0.15Co0.85Si, and 8.3% for Fe0.26Co0.74Si. These enhancements of the ξSH can be attributed to the improvement in the interfacial spin transparency between the Co(Ni, Fe)Si and CoFeB layers.

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Section: Resultsmentioning

confidence: 99%

\begin{array}{*{20}{c}}{V = {V_{\rm{S}}}\frac{{{\Delta ^2}}}{{{{\left( {H - {H_{{\rm{res}}}}} \right)}^2} + {\Delta ^2}}} + {V_{\rm{A}}}\frac{{\Delta \left( {H - {H_{{\rm{res}}}}} \right)}}{{{{\left( {H - {H_{{\rm{res}}}}} \right)}^2} + {\Delta ^2}}} + C}\end{array}

Section: Resultsmentioning

confidence: 99%

Elemental Doping and Interface Effects on Spin–Orbit Torques in CoSi‐Based Topological Semimetal Thin Films

Wen

Seki

et al. 2022

Adv Materials Inter

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“…Since the spin currents we consider produce a spin-torque within a few atomic spacings of an interface, the spin current's action on a free layer may further be affected by interface-related inhomogeneous spinexcitation processes. The materials physics origins of many such measurement inconsistencies are being actively investigated [90,[95][96][97].…”

Section: Metric and Measurement Of Sot-generated Spin Currentsmentioning

confidence: 99%

A Perspective on Electrical Generation of Spin Current for Magnetic Random Access Memories

Safranski,

Sun,

Kent

2022

Preprint

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Spin currents are used to write information in magnetic random access memory (MRAM) devices by switching the magnetization direction of one of the ferromagnetic electrodes of a magnetic tunnel junction (MTJ) nanopillar. Different physical mechanisms of conversion of charge current to spin current can be used in 2-terminal and 3-terminal device geometries. In 2-terminal devices, charge-to-spin conversion occurs by spin filtering in the MTJ's ferromagnetic electrodes and present day MRAM devices operate near the theoretically expected maximum charge-to-spin conversion efficiency. In 3-terminal devices, spin-orbit interactions in a channel material can also be used to generate large spin currents. In this perspective article, we discuss charge-to-spin conversion processes that can satisfy the requirements of MRAM technology. We emphasize the need to develop channel materials with larger charge-to-spin conversion efficiency-that can equal or exceed that produced by spin filtering-and spin currents with a spin polarization component perpendicular to the channel interface. This would enable high-performance devices based on sub-20 nm diameter perpendicularly magnetized MTJ nanopillars without need of a symmetry breaking field. We also discuss MRAM characteristics essential for CMOS integration. Finally, we identify critical research needs for charge-to-spin conversion measurements and metrics that can be used to optimize device channel materials and interface properties prior to full MTJ nanopillar device fabrication and characterization.

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“…The work-horse techniques for this purpose have been electrical measurements of current-induced magnetic reorientation with readout based on the magnetoresistance properties of the samples (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19), but these have some shortcomings. One must be careful to separate thermoelectric voltages from the torque signals (20,21), and, even when performed carefully, different electrical techniques can often produce quantitatively inconsistent measurements, indicating that some may be affected by artifacts that are not yet understood (22)(23)(24)(25)(26). Furthermore, in cases when one wishes to measure SOTs acting on insulating magnetic layers, electrical measurements provide much lower signal levels compared to metallic magnets due to decreased magnetoresistance.…”

Section: Introductionmentioning

confidence: 99%

Sagnac interferometry for high-sensitivity optical measurements of spin-orbit torque

Karimeddiny,

Cham,

Smedley

et al. 2023

Sci. Adv.

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Sagnac interferometry can provide a substantial improvement in signal-to-noise ratio compared to conventional magnetic imaging based on the magneto-optical Kerr effect. We show that this improvement is sufficient to allow quantitative measurements of current-induced magnetic deflections due to spin-orbit torque even in thin-film magnetic samples with perpendicular magnetic anisotropy, for which the Kerr rotation is second order in the magnetic deflection. Sagnac interferometry can also be applied beneficially for samples with in-plane anisotropy, for which the Kerr rotation is first order in the deflection angle. Optical measurements based on Sagnac interferometry can therefore provide a cross-check on electrical techniques for measuring spin-orbit torque. Different electrical techniques commonly give quantitatively inconsistent results so that Sagnac interferometry can help to identify which techniques are affected by unidentified artifacts.

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Resolving Discrepancies in Spin-Torque Ferromagnetic Resonance Measurements: Lineshape versus Linewidth Analyses

Cited by 9 publications

References 22 publications

Elemental Doping and Interface Effects on Spin–Orbit Torques in CoSi‐Based Topological Semimetal Thin Films

Elemental Doping and Interface Effects on Spin–Orbit Torques in CoSi‐Based Topological Semimetal Thin Films

A Perspective on Electrical Generation of Spin Current for Magnetic Random Access Memories

Sagnac interferometry for high-sensitivity optical measurements of spin-orbit torque

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