Deterministic Domain Wall Motion Orthogonal To Current Flow Due To Spin Orbit Torque

Bhowmik, Debjit; Nowakowski, Mark E.; You, Long; Lee, OukJae; Keating, David; Wong, Mark; Bokor, Jeffrey; Salahuddin, Sayeef

doi:10.1038/srep11823

Cited by 73 publications

(66 citation statements)

References 36 publications

(86 reference statements)

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“…We believe that, although the existence of dH an /dy gradient-induced fieldlike SOT [27] cannot be completely ruled out, a major contribution of the measured χ Wedged originates from the asymmetric nature of nucleation/depinning process in these wedged-deposited Pt/Co/MgO devices. If this is the case, then further studies on the interplay among structural factors, especially the DMI [43] and the current-induced (Oersted) field [44][45][46] at the edges in these magnetic heterostructures, will be beneficial for engineering SOT switching without external bias field. To summarize, we demonstrate that by characterizing the shift of out-of-plane hysteresis loops under different dc currents and in-plane bias fields, the SOT efficiency χ = H z eff /J e ≈ χ SHE for Pt/Co/MgO, Pt/CoFeB/MgO, and Ta/CoFeB/MgO heterostructures can be obtained.…”

mentioning

confidence: 99%

Determination of spin torque efficiencies in heterostructures with perpendicular magnetic anisotropy

Pai¹,

Mann²,

Tan³

et al. 2016

Phys. Rev. B

306

304

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We report that by measuring a current-induced hysteresis loop shift versus in-plane bias magnetic field, the spin-Hall effect (SHE) contribution of the current-induced effective field per current density χ SHE can be estimated for Pt-and Ta-based magnetic heterostructures with perpendicular magnetic anisotropy. We apply this technique to a Pt-based sample with its ferromagnetic (FM) layer being wedged deposited and discover an extra effective field contribution χ Wedged due to the asymmetric nature of the deposited FM layer. We confirm the correlation between χ Wedged and the asymmetric depinning process in FM layer during magnetization switching by magneto-optical Kerr microscopy. These results indicate the possibility of engineering deterministic spin-orbit torque switching by controlling the symmetry of domain expansion through the materials growth process. DOI: 10.1103/PhysRevB.93.144409 Current-induced spin-orbit torque (SOT) has been shown to be an efficient way of manipulating the magnetization in heavy-metal/ferromagnet (HM/FM) heterostructures. Unlike conventional spin transfer torque [1,2] in which the source of spin angular momentum comes from a ferromagnetic polarizer layer, SOTs arise from either the bulklike spin-Hall effect (SHE) [3,4] of the nonmagnetic (NM) HM layer or Rashbatype spin-orbit interaction [5,6] at the interface. SOTs can be utilized to achieve efficient magnetization switching [7][8][9][10], ultrafast domain-wall (DW) motion [6,11,12], and microwave generation through magnetic oscillations [13,14] in spintronic device applications.SOTs are typically studied in magnetic heterostructures with perpendicular magnetic anisotropy (PMA), and in general both a Slonczewski-like and a field-like torque can be present. The Slonczewski-like torque is most relevant to magnetization switching: It manifests as an effective field H eff with an out-of-plane (easy-axis) component that can reverse the magnetization or drive DWs if a component of the magnetization lies along the current-flow direction. The most common measurement schemes used to quantify the Slonczewski-like SOT efficiency χ ≡ H eff /J e (effective field per unit current density J e ) include ferromagnetic resonance techniques [15][16][17], low-frequency harmonic voltage measurements using small ac currents [18][19][20], and analysis of current-induced DW motion in thin magnetic strips [11,12,21,22]. Current-induced SOT switching of PMA films under an in-plane bias field is another convenient means for determining the sign of χ ; however, a quantitative estimate of its magnitude is usually difficult to obtain in such measurements due to the complicated magnetization reversal process [23,24].In this paper we examine the role of domain nucleation and DW propagation in SOT-assisted magnetization switching in HM/FM bilayer systems with PMA. We show that the currentinduced shift of the out-of-plane hysteresis loop as a function of in-plane bias field can be well explained by a simple currentassisted DW propagation model. This simple mea...

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mentioning

confidence: 99%

Determination of spin torque efficiencies in heterostructures with perpendicular magnetic anisotropy

Pai¹,

Mann²,

Tan³

et al. 2016

Phys. Rev. B

306

304

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“…In most experimental cases, the samples prepared are micron-sized and the magnetization switching process is dominated by domain nucleation and domain wall propagation [23,29,38]. Therefore, in our case, the critical switching current density should be expressed as In contrast to the Cu-Ta alloy case, in which the buffer layer resistivity is lower than that of pure Ta, we further engineered the buffer layer by nitrogen-doping to see the effects on resistivity enhancement.…”

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confidence: 99%

Tunable spin-orbit torque in Cu-Ta binary alloy heterostructures

Chen¹,

Wu²,

Yen³

et al. 2017

Phys. Rev. B

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The spin Hall effect (SHE) is found to be strong in heavy transition metals (HM), such as Ta and W, in their amorphous and/or high resistivity form. In this work, we show that by employing a CuTa binary alloy as buffer layer in an amorphous Cu100-xTax-based magnetic heterostructure with perpendicular magnetic anisotropy (PMA), the SHE-induced damping-like spin-orbit torque (DL-SOT) efficiency DL  can be linearly tuned by adjusting the buffer layer resistivity. Currentinduced SOT switching can also be achieved in these Cu100-xTax-based magnetic heterostructures, and we find the switching behavior better explained by a SOT-assisted domain wall propagation picture. Through systematic studies on Cu100-xTax-based samples with various compositions, we determine the lower bound of spin Hall conductivity

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“…Spin-orbit torques (SOT) effect has been demonstrated as a promising technique to control the magnetization in heavy metal (HM)/ferromagnetic metal (FM) heterostructures12345678. An in-plane electric current applied to the heterostructures with large spin–orbit coupling (SOC) and structural inversion asymmetry gives rise to the torques, which induces magnetization switching under an external magnetic field collinear with the current.…”

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confidence: 99%

Modulated switching current density and spin-orbit torques in MnGa/Ta films with inserting ferromagnetic layers

Meng

Miao

et al. 2016

Sci Rep

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We report modulated switching current density and spin-orbit torques (SOT) in MnGa/Ta films with inserting very thin Co2FeAl and Co layers. Ferromagnetic coupling has been found in MnGa/Co2FeAl/Ta, resulting in a decreased effective anisotropy field. On the contrary, in MnGa/Co/Ta, antiferromagnetic coupling plays a dominant role. The switching current density Jc in MnGa/Ta is 8.5 × 107 A/cm2. After inserting 0.8-nm-thick Co2FeAl and Co, theJc becomes 5 × 107 A/cm2 and 9 × 107 A/cm2, respectively. By performing adiabatic harmonic Hall voltage measurements, it is demonstrated that the inserted Co2FeAl layer has mainly enhanced the field-like torques, while in MnGa/Co/Ta the damping-like torques have been enhanced. Finally, the enhanced spin Hall effect (SHE) has also been studied using the spin Hall magnetoresistance measurement. The modulated Jc and SOT are ascribed to the combination of magnetic coupling, Rashba effect and SHE at the interfaces.

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Deterministic Domain Wall Motion Orthogonal To Current Flow Due To Spin Orbit Torque

Cited by 73 publications

References 36 publications

Determination of spin torque efficiencies in heterostructures with perpendicular magnetic anisotropy

Determination of spin torque efficiencies in heterostructures with perpendicular magnetic anisotropy

Tunable spin-orbit torque in Cu-Ta binary alloy heterostructures

Modulated switching current density and spin-orbit torques in MnGa/Ta films with inserting ferromagnetic layers

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