Temperature dependence of the spin Hall angle and switching current in the nc-W(O)/CoFeB/MgO system with perpendicular magnetic anisotropy

Neumann, Lukáš; Meier, Daniel; Schmalhorst, Jan-Michael; Rott, Karsten; Reiss, Günter; Meinert, Markus

doi:10.1063/1.4964415

Cited by 27 publications

(18 citation statements)

References 25 publications

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“…The magnitude of the Spin Hall conductivity as a function of tungsten film thickness is shown for a variety of experimental measurements 4,5,37,41,42,[50][51][52][53][54] and theoretical predictions 6,47 . The calculated bulk intrinsic SHC for pristine β-W is shown at the Fermi energy (red dashed line) and for maximum possible value with p-type doping (black dashed line).…”

Section: Figmentioning

confidence: 99%

Impact of impurities on the spin Hall conductivity in β -W

McHugh

Goh

Gradhand

et al. 2020

Phys. Rev. Materials

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While the metastable β (A15) phase of tungsten has one of the largest spin Hall angles measured, the origin of this high spin Hall conductivity is still unclear. Since large concentrations of oxygen and nitrogen are often used to stabilize β tungsten, it is not obvious whether the high spin Hall conductivity is due to an intrinsic or extrinsic effect. In this work, we have examined the influence of O and N dopants on the spin Hall conductivity and spin Hall angle of β-W. Using multiple first principles approaches, we examine both the intrinsic and extrinsic (skew scattering) contributions to spin Hall conductivity. We find that intrinsic spin Hall conductivity calculations for pristine β-W are in excellent agreement with experiment. However, when the effect of high concentrations (11 at.%) of O or N interstitials on the electronic structures is taken into account, the predicted intrinsic spin Hall conductivity is significantly reduced. Skew scattering calculations for O and N interstitials in β-W indicate that extrinsic contributions have a limited impact on the total spin Hall conductivity. However, we find that the spin-flip scattering at O and N impurities can well explain the experimentally found spin-diffusion length within the range of 1-5 nm. To explain these findings, we propose that dopants (O and N) help to stabilize β-W grains during film deposition and afterwards segregate to the grain boundaries. This process leads to films of relatively pristine small β-W grains and grain boundaries with high concentrations of O or N scattering sites. This combination provides high spin Hall conductivity and large electrical resistance, leading to high spin Hall angles. This work shows that engineering grain boundary properties in other high spin Hall conductivity materials could provide an effective way to boost the spin Hall angle.

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Section: Figmentioning

confidence: 99%

Impact of impurities on the spin Hall conductivity in β -W

McHugh

Goh

Gradhand

et al. 2020

Phys. Rev. Materials

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“…Spin–orbit torques (SOTs) in ferromagnet/heavy metal bilayers can be utilized to electrically manipulate and switch the magnetization in the magnetic layer . In these systems, the spin Hall effect in the heavy metal layer and electron scattering at the interface induce a spin current from the heavy metal to the adjacent magnetic layer, which gives rise to SOT.…”

Section: Introductionmentioning

confidence: 99%

Co‐sputtered PtMnSb thin films and PtMnSb/Pt bilayers for spin–orbit torque investigations

Krieft

Mendil

Aguirre

et al. 2017

Physica Rapid Research Ltrs

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The manipulation of the magnetization by spin–orbit torques (SOTs) has recently been extensively studied due to its potential for efficiently writing information in magnetic memories. Particular attention is paid to non‐centrosymmetric systems with space inversion asymmetry, where SOTs emerge even in single‐layer materials. The half‐metallic half‐Heusler PtMnSb is an interesting candidate for studies of this intrinsic SOT. Here, we report on the growth and epitaxial properties of PtMnSb thin films and PtMnSb/Pt bilayers deposited on MgO(001) substrates by dc magnetron co‐sputtering at high temperature in ultra‐high vacuum. The film properties were investigated by X‐ray diffraction, X‐ray reflectivity, atomic force microscopy, and electron microscopy. Thin PtMnSb films present a monocrystalline C1b phase with (001) orientation, coexisting at increasing thickness with a polycrystalline phase with (111) texture. Films thinner than about 5 nm grow in islands, whereas thicker films grow ultimately layer‐by‐layer, forming a perfect MgO/PtMnSb interface. The thin PtMnSb/Pt bilayers also show island growth and a defective transition zone, while thicker films grow layer‐by‐layer and Pt grows epitaxially on the half‐Heusler compound without significant interdiffusion.

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“…We expect because the formula is based on the macro spin model as like well-known Brown paradox 38 . Furthermore, there are reports that it does not match the actual value in the micron scale sample 39,40 . That's why we obtained θ SH from the spin-orbit torque effective eld measurement (see Figure 5c), not from the switching current density.…”

Section: Resultsmentioning

confidence: 94%

Improved Spin-orbit Torque Induced Magnetization Switching Efficiency by Helium Ion Irradiation

Baek

Kim

et al. 2021

Preprint

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Increasing the efficiency of spin-orbit torque (SOT) is of great interest in spintronics devices because of its application to the non-volatile magnetic random access memory and in-logic memory devices. Accordingly, there are several studies to alter the magnetic properties and reduce the SOT switching current with Helium ion irradiation, but previous researches are focused on its quantitative changes only. Here, the authors observe the reduction of switching current and analyze the origins of Helium ion irradiation induced SOT switching current reduction. The first is from improved spin Hall angle caused by the resistivity change of heavy metal layer and second is from the reduction of surface anisotropy energy at interface between heavy metal and ferromagnet. The result shows that switching current is reduced about ~30.3% at dose of 30 ions/nm2 and relevant parameter change is shown as improved spin Hall angle from 0.096 to 0.132 and reduced anisotropy field from 13.7 to 8.5 kOe. Altogether, the power consumption ratio is calculated based on the derived parameter and result shows that requiring power reaches only 56.0% at 30 ions/nm2. This analysis suggests that more efficient SOT device engineering is possible by Helium ion irradiation.

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Temperature dependence of the spin Hall angle and switching current in the nc-W(O)/CoFeB/MgO system with perpendicular magnetic anisotropy

Cited by 27 publications

References 25 publications

Impact of impurities on the spin Hall conductivity in β -W

Impact of impurities on the spin Hall conductivity in β -W

Co‐sputtered PtMnSb thin films and PtMnSb/Pt bilayers for spin–orbit torque investigations

Improved Spin-orbit Torque Induced Magnetization Switching Efficiency by Helium Ion Irradiation

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