Field-free magnetization switching induced by the unconventional spin–orbit torque from WTe2

Xie, Qidong; Lin, Weinan; Sarkar, Soumya; Shu, Xinyu; Liu, Liang; Zhao, Tieyang; Zhou, Chang; Wang, Han; Zhou, Jing; Gradečak, Silvija; Chen, Jingsheng

doi:10.1063/5.0048926

Cited by 41 publications

(23 citation statements)

References 31 publications

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“…The chiral symmetry breaking by a gradient of magnetic anisotropy or saturation magnetization can also induce field-free switching 15 . Different from the above approaches that require asymmetric designs in device/film structures, recent works utilized the crystal symmetry to engineer the field-free switching in the WTe 2 /FM bilayer 16 – 18 and the CuPt/FM bilayer 19 . Although largely explored, the existing field-free switching in the above SOT bilayers/trilayers has some intrinsic disadvantages.…”

Section: Introductionmentioning

confidence: 99%

Current-induced self-switching of perpendicular magnetization in CoPt single layer

et al. 2022

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All-electric switching of perpendicular magnetization is a prerequisite for the integration of fast, high-density, and low-power magnetic memories and magnetic logic devices into electric circuits. To date, the field-free spin-orbit torque (SOT) switching of perpendicular magnetization has been observed in SOT bilayer and trilayer systems through various asymmetric designs, which mainly aim to break the mirror symmetry. Here, we report that the perpendicular magnetization of CoxPt100-x single layers within a special composition range (20 < x < 56) can be deterministically switched by electrical current in the absence of external magnetic field. Specifically, the Co30Pt70 shows the largest out-of-plane effective field efficiency and best switching performance. We demonstrate that this unique property arises from the cooperation of two structural mechanisms: the low crystal symmetry property at the Co platelet/Pt interfaces and the composition gradient along the thickness direction. Compared with that in bilayers or trilayers, the field-free switching in CoxPt100-x single layer greatly simplifies the SOT structure and avoids additional asymmetric designs.

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Section: Introductionmentioning

confidence: 99%

Current-induced self-switching of perpendicular magnetization in CoPt single layer

et al. 2022

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“…Development of high-density magnetic memory and computing technologies requires energy-efficient and scalable electrical switching of perpendicular magnetization. Microscopically, perpendicular magnetization can be switched by a current of transverse spins (σy) under the assist of an in-plane effective magnetic field along current (𝐻 𝑥 eff , to overcome the Dzyaloshinskii-Moriya interaction or to break the switching symmetry) 1 , or by an antidamping spin torque exerted by high-density current of perpendicular spins (σz) [2][3][4][5][6][7][8][9][10] , or by a strong perpendicular effective magnetic field (𝐻 𝑧 eff ) [11][12][13][14][15] . Since the first method (σy+𝐻 𝑥 eff ) is hardly energy-efficient or scalable, searching of σz or 𝐻 𝑧 eff in magnetic heterostructures becomes a very hot topic.…”

Section: Introductionmentioning

confidence: 99%

Current-induced perpendicular effective magnetic field in magnetic heterostructures

Liu

Zhu

2022

Applied Physics Reviews

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The generation of perpendicular effective magnetic field or perpendicular spins ( σz) is central for the development of energy-efficient, scalable, and external-magnetic-field-free spintronic memory and computing technologies. Here, we report the first identification and the profound impacts of a significant effective perpendicular magnetic field that can arise from asymmetric current spreading within magnetic microstrips and Hall bars. This effective perpendicular magnetic field can exhibit all the three characteristics that have been widely assumed in the literature to “signify” the presence of a flow of σz, i.e., external-magnetic-field-free current switching of uniform perpendicular magnetization, a sin 2 φ-dependent contribution in spin-torque ferromagnetic resonance signal of in-plane magnetization ( φ is the angle of the external magnetic field with respect to the current), and a φ-independent but field-dependent contribution in the second harmonic Hall voltage of in-plane magnetization. This finding suggests that it is critical to include current spreading effects in the analyses of various spin polarizations and spin–orbit torques in the magnetic heterostructure. Technologically, our results provide a perpendicular effective magnetic field induced by asymmetric current spreading as a novel, universally accessible mechanism for efficient, scalable, and external-magnetic-field-free magnetization switching in memory and computing technologies.

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“…In this scenario, the spin electrons in the Pt layer with polarization along + p y (or − p y ) have been realigned, causing the spin polarization with an out-of-plane component. To confirm the existence and contribution of the out-of-plane spin-orbit torque contribution to the field-free SOT switching in the particular system, , we carried out the measurements with shifting V xy loops under different DC currents I DC . Figure a,b shows the V xy shift loops for MgO/Pt/Co samples at H x = 0 and H x = 520 Oe, respectively.…”

Section: Resultsmentioning

confidence: 99%

Spin Reflection-Induced Field-Free Magnetization Switching in Perpendicularly Magnetized MgO/Pt/Co Heterostructures

Jin

Lim

Poh

et al. 2022

ACS Appl. Mater. Interfaces

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Field-free magnetization switching is critical towards practical, integrated spin-orbit torque (SOT)-driven magnetic random-access memory with perpendicular magnetic anisotropy. Our work proposes a technique to modulate the spin reflection and spin density of states within a heavy-metal Pt through interfacing with a dielectric MgO layer. We demonstrate tunability of the effective out-of-plane spin torque acting on the ferromagnetic Co layer, enabling current-induced SOT magnetization switching without the assistance of an external magnetic field. The influence of the MgO layer thickness on effective SOT efficiency shows saturation at 4 nm, while up to 80% of field-free magnetization switching ratio is achieved with the MgO between 5 and 8 nm. We analyze and attribute the complex interaction to spin reflection at the dielectric/heavy metal interface and spin scattering within the dielectric medium due to interfacial electric fields. Further, through substituting the dielectric with Ti or Pt, we confirm that the MgO layer is indeed responsible for the observed field-free magnetization switching mechanism.

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Field-free magnetization switching induced by the unconventional spin–orbit torque from WTe2

Cited by 41 publications

References 31 publications

Current-induced self-switching of perpendicular magnetization in CoPt single layer

Current-induced self-switching of perpendicular magnetization in CoPt single layer

Current-induced perpendicular effective magnetic field in magnetic heterostructures

Spin Reflection-Induced Field-Free Magnetization Switching in Perpendicularly Magnetized MgO/Pt/Co Heterostructures

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