Enhanced spin-orbit torque by engineering Pt resistivity in 
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Lee, Jae Woo; Oh, Young Wan; Park, Seung Young; Figueroa, A. I.; Laan, G. van der; Go, Gyungchoon; Lee, Kyung Jin; Park, Byong‐Guk

doi:10.1103/physrevb.96.064405

Cited by 73 publications

(38 citation statements)

References 43 publications

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“…In Fig. 4, such an enhanced STT efficiency was achieved by optimizing the Pt thickness compared to the reported results [14,15,[19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Both axis are the transverse component and longitudinal component of the STT efficiency.…”

Section: Resultsmentioning

confidence: 72%

“…We experimentally demonstrated that the STT efficiency in Ta/Pt/FM structures can be enhanced while the Pt layer has a specific thickness. The enhanced STT efficiency is almost 4 times larger than those reported [14,20,24,27,31,32]. Our work provides a new approach to further reduce power consumption in magnetization switching.…”

Section: Introductionmentioning

confidence: 73%

“…The square shape in the Hall resistance was attributed to the anomalous Hall effect induced by the magnetization with PMA. Thus, we are allowed to evaluate the STT efficiency using harmonic Hall measurment [19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”

Section: Charge-spin Conversion and Spin Diffusionmentioning

confidence: 99%

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Enhanced spin transfer torque in platinum/ferromagnetic-metal structures by optimizing the platinum thickness

Xue

Guo

Wang

et al. 2020

Journal of Magnetism and Magnetic Materials

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Spin transfer torque (STT) driven by a charge current plays a key role in magnetization switching in heavy-metal/ferromagnetic-metal structures. The STT efficiency defined by the ratio between the effective field due to STT and the current density, is required to be improved to reduce energy compulsions in the STT-based spintronic devices. In this work, using the harmonic Hall measurement method, we experimentally studied the STT efficiency in platinum(Pt)/FM structures as a function of the Pt thickness. We found that the STT efficiency strongly depends on the Pt thickness and reaches a maximum value of 4.259 mT/(10 6 A/cm 2 ) for the 1.8-nm-thickness Pt sample. This result indicates that competition between spin Hall effect (SHE) and Rashba effect as well as spin diffusion process across the Pt layer determines the Pt thickness for the maximum STT efficiency. We demonstrated the role played by the spin diffusion besides the spin current generation mechanisms in improvement of the STT efficiency, which is helpful in designing STT-based devices.

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Section: Resultsmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 73%

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Enhanced spin transfer torque in platinum/ferromagnetic-metal structures by optimizing the platinum thickness

Xue

Guo

Wang

et al. 2020

Journal of Magnetism and Magnetic Materials

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“…To confirm the thickness dependence of the SOT shown in Figure 3, we first test the SOT-induced switching of the samples with different values of t Ta under B x = +50 mT. Thus, the overall trend of the switching current versus t Ta is qualitatively consistent with that of the B DL , [30,31,36] but the t Ta for the largest switching efficiency (or smallest switching current) is slightly smaller than the t Ta for the largest B DL (Figure 3). Moreover, the switching currents of both samples are smallest for t Ta of 1.5-2 nm and increase with either increasing or decreasing t Ta .…”

Section: Current-induced Switching Of Perpendicular Magnetizationmentioning

confidence: 59%

“…Since the SOT exerted on the top CoFeB layer is of interest, we remove the contribution of the bottom FM layers to V 1ω and V 2ω . Between the two sources of SOT, SHE in HM and interface-generated spin current of FM/HM [8,[21][22][23]29,30] in the FM/Ta/CoFeB trilayer structures, the latter dominates for thin HM, while the former dominates for thick HM. [4,24] Moreover, V 2ω is modified by removing the anomalous Nernst voltage of the bottom FM layers induced by vertical temperature gradient, [4,21,28] which is not relevant to the SOT.…”

Section: Introductionmentioning

confidence: 99%

Material and Thickness Investigation in Ferromagnet/Ta/CoFeB Trilayers for Enhancement of Spin–Orbit Torque and Field‐Free Switching

Ryu

Kang

et al. 2019

Adv Elect Materials

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in-plane (perpendicular) magnetic anisotropy. The spin current generated from the FM/Ti interface has a spin polarization along the m × y direction, where m is the magnetization direction of the bottom FM. For an FM with m aligned in the x-direction, a spin current with zspin polarization is generated. [22,23] This enables field-free SOT switching of the perpendicular magnetization of the top CoFeB layer.In this work, we investigate the SOTs in FM/Ta/CoFeB trilayers, in which the spin current generated by SHE in Ta can be combined with the interface-generated spin currents. Using various Ta thickness, we perform measurements of SOTinduced effective fields and of magnetization switching with various Ta thicknesses. We observe two interesting points for a sample with a thin Ta layer; first, the sign of the SOT is determined by the bottom FM layer, and is positive for NiFe and negative for CoFeB. Second, SOT-induced switching is achieved without an in-plane magnetic field. These results demonstrate that the interface-generated spin current of the FM/Ta bilayer governs the SOT of a sample with a thin Ta layer. On the other hand, as Ta thickness increases, the sign of the SOT becomes negative irrespective of the bottom FM and which is determined by the Ta, which has a negative spin Hall angle. This demonstrates that the SOT in the trilayer structure is composed of two contributions: SHE in HM and interface-generated spin current of the FM/HM bilayer, suggesting that the proper selection of an FM/HM combination and of the material thickness can enhance the SOT efficiency and induce field-free SOT switching. Results and Discussion Spin-Orbit Torques in FM/Ta/CoFeB TrilayersIn order to investigate SOT in FM/Ta/CoFeB trilayer structures, we employ Ta (5 nm)/FM (4 nm)/Ta (t Ta )/CoFeB (1.0 nm)/ MgO (3.2 nm) structures, where Ta thickness (t Ta ) ranges from 1.0 to 6.0 nm (Figure 1a). The bottom FM is in-plane magnetized CoFeB or NiFe. As the samples share identical material structures, except for the bottom FM, we refer to the trilayer CoFeB or NiFe samples according to the bottom FM layers. We first check the magnetic anisotropy of each layer by Spin-orbit torques (SOTs) in ferromagnet (FM)/Ta/CoFeB trilayers are investigated as a function of Ta thickness. When the Ta is thinner than 1.5 nm, the sign of the SOT exerting on the top perpendicularly magnetized CoFeB depends on the bottom FM layer; it is positive for NiFe and negative for CoFeB. As the Ta thickness increases, the sign becomes negative irrespective of the bottom FM, indicating that SOTs are dominated by Ta, which has a negative spin Hall angle. SOT-induced switching without an in-plane magnetic field is observed in the thickness ranges where the bottom FM or FM/Ta interface-generated SOT is dominant. The results herein demonstrate that proper design of an FM/heavy metal combination and the material thickness can lead to an enhancement of the SOT efficiency and allow for field-free SOT switching.

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Strong Damping‐Like Spin‐Orbit Torque and Tunable Dzyaloshinskii–Moriya Interaction Generated by Low‐Resistivity Pd₁₋_xPt_x Alloys

Zhu

Sobotkiewich

et al. 2019

Adv Funct Materials

133

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Despite their great promise for providing a pathway for very efficient and fast manipulation of magnetization, spin-orbit torque (SOT) operations are currently energy inefficient due to a low damping-like SOT efficiency per unit current bias, and/or the very high resistivity of the spin Hall materials. This work reports an advantageous spin Hall material, Pd 1−x Pt x , which combines a low resistivity with a giant spin Hall effect as evidenced with three independent SOT ferromagnetic detectors. The optimal Pd 0.25 Pt 0.75 alloy has a giant internal spin Hall ratio of >0.60 (damping-like SOT efficiency of ≈0.26 for all three ferromagnets) and a low resistivity of ≈57.5 µΩ cm at a 4 nm thickness. Moreover, it is found that the Dzyaloshinskii-Moriya interaction (DMI), the key ingredient for the manipulation of chiral spin arrangements (e.g., magnetic skyrmions and chiral domain walls), is considerably strong at the Pd 1−x Pt x /Fe 0.6 Co 0.2 B 0.2 interface when compared to that at Ta/Fe 0.6 Co 0.2 B 0.2 or W/Fe 0.6 Co 0.2 B 0.2 interfaces and can be tuned by a factor of 5 through control of the interfacial spin-orbital coupling via the heavy metal composition. This work establishes a very effective spin current generator that combines a notably high energy efficiency with a very strong and tunable DMI for advanced chiral spintronics and spin torque applications.

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Enhanced spin-orbit torque by engineering Pt resistivity in Pt/Co/AlOx structures

Cited by 73 publications

References 43 publications

Enhanced spin transfer torque in platinum/ferromagnetic-metal structures by optimizing the platinum thickness

Enhanced spin transfer torque in platinum/ferromagnetic-metal structures by optimizing the platinum thickness

Material and Thickness Investigation in Ferromagnet/Ta/CoFeB Trilayers for Enhancement of Spin–Orbit Torque and Field‐Free Switching

Strong Damping‐Like Spin‐Orbit Torque and Tunable Dzyaloshinskii–Moriya Interaction Generated by Low‐Resistivity Pd₁₋_xPt_x Alloys

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Enhanced spin-orbit torque by engineering Pt resistivity in Pt/Co/AlOx structures

Cited by 73 publications

References 43 publications

Enhanced spin transfer torque in platinum/ferromagnetic-metal structures by optimizing the platinum thickness

Enhanced spin transfer torque in platinum/ferromagnetic-metal structures by optimizing the platinum thickness

Material and Thickness Investigation in Ferromagnet/Ta/CoFeB Trilayers for Enhancement of Spin–Orbit Torque and Field‐Free Switching

Strong Damping‐Like Spin‐Orbit Torque and Tunable Dzyaloshinskii–Moriya Interaction Generated by Low‐Resistivity Pd1−xPtx Alloys

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Resources

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Strong Damping‐Like Spin‐Orbit Torque and Tunable Dzyaloshinskii–Moriya Interaction Generated by Low‐Resistivity Pd₁₋_xPt_x Alloys