Efficient Spin–Orbit Torque Switching with Nonepitaxial Chalcogenide Heterostructures

Chen, Tian-Yue; Peng, Chian Yu; Tsai, Tsung-Yu; Liao, Wanjiun; Wu, Cheng-En; Yen, Hung‐Wei; Pai, Chi‐Feng

doi:10.1021/acsami.9b20844

Cited by 33 publications

(18 citation statements)

References 39 publications

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“…Thus, it is crucial to investigate the SOT performance of non-epitaxial TI thin films on Si/SiO 2 wafers. Recently, there are attempts to deposit and evaluate the performance of non-epitaxial Bi x Se 1-x and Bi x Te 1-x thin films by sputtering on Si/SiO 2 substrates, which show promising results 26,27 . In particular, Bi x Se 1-x shows a very large θ SH = 8.7-18.6 but with the expense of reduced electrical conductivity (~ 7.8 × 10 3 Ω −1 m −1 ) comparing with epitaxial Bi 2 Se 3 (~ 5.7 × 10 4 Ω −1 m −1 ).…”

mentioning

confidence: 99%

Ultralow power spin–orbit torque magnetization switching induced by a non-epitaxial topological insulator on Si substrates

Khang

Nakano

Shirokura

et al. 2020

Sci Rep

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The large spin Hall effect in topological insulators (TIs) is very attractive for ultralow-power spintronic devices. However, evaluation of the spin Hall angle and spin-orbit torque (SOT) of TIs is usually performed on high-quality single-crystalline TI thin films grown on dedicated III-V semiconductor substrates. Here, we report on room-temperature ultralow power SOT magnetization switching of a ferrimagnetic layer by non-epitaxial BiSb TI thin films deposited on Si/SiO 2 substrates. We show that non-epitaxial BiSb thin films outperform heavy metals and other epitaxial TI thin films in terms of the effective spin Hall angle and switching current density by one to nearly two orders of magnitude. The critical SOT switching current density in BiSb is as low as 7 × 10 4 A/cm 2 at room temperature. The robustness of BiSb against crystal defects demonstrate its potential applications to SOT-based spintronic devices. Charge-to-spin conversion utilizing the strong spin-orbit coupling (SOC) in non-magnetic materials has become a very attractive concept with possible applications to various spintronic devices, such as spin-orbit torque (SOT) magnetoresistive random access memories (MRAM) 1 , racetrack memories 2 , and spin torque nano-oscillators 3,4. These SOT-based spintronic devices are superior to their spin-transfer torque (STT)-based counterparts in terms of driving current, speed, and long-term durability 5,6. In SOT-based devices, a perpendicular pure spin current density J s is generated by an in-plane charge current density J e in the non-magnetic layer through the spin Hall effect (SHE) 7-9 , whose charge-to-spin conversion efficiency is characterized by the spin Hall angle θ SH = (2e/ℏ) J s /J e. Thus, finding spin Hall materials with large θ SH and high electrical conductivity is crucial for SOT applications, and there have been huge efforts so far to achieve that goal. In the well-studied heavy metals (HMs) such as Pt 10-13 , Ta 14 , and W 15-17 , θ SH is of the order of ~ 0.1, and the typical critical switching current density J c in bilayers of heavy metals/ferromagnet with perpendicular magnetic anisotropy is typically of the order of 10 7 A/cm 2 for continuous direct currents (DC) and 10 8 A/cm 2 for nano-second (ns) pulse currents. The large switching current density requires large driving transistors, whose size limits the bit density of SOT-MRAM. Meanwhile, large θ SH (> 1) have been observed in topological insulators (TIs) 18,19 thanks to their strong SOC and Dirac-point-driven singularity of the Berry phase on their topologically protected surface states 20. Thus, significant reduction of the driving current density from 10 7-10 8 A/cm 2 to 10 5-10 6 A/cm 2 can be expected for SOT-based devices 21-25 , particularly in SOT-MRAM whose their large writing current density is the major obstacle for reducing the writing power consumption and increasing the bit density. However, evaluation of θ SH and SOT switching by TIs is usually performed on single-crystalline TI thin films deposited on dedicated III-V...

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mentioning

confidence: 99%

Ultralow power spin–orbit torque magnetization switching induced by a non-epitaxial topological insulator on Si substrates

Khang

Nakano

Shirokura

et al. 2020

Sci Rep

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“…( 2 ), respectively. Figure 7 d shows the relationship between the extracted values of H DL and J YPtBi for sample F. From the slope H DL / J YPtBi , M S = 443 emu/cc and t CoPt = 1.3 nm, we obtain = 4.1 for sample F, which is not only 2.6 times larger than that in sample E but also larger than that of several conventional TIs such as Bi 2 Se 3 , (BiSb) 2 Te 3 , and Bi x Te 1-x 9 , 10 , 12 . Note that, the improvement factor of 2.6 cannot be explained only by the elimination of spin dissipation in the Pt interfacial layer, which is given by = 0.78, where t Pt and of 1.1 nm are thickness and spin diffusion length for Pt, respectively.…”

Section: Further Improvement Of Spin Hall Anglementioning

confidence: 68%

“…On the hand, TIs with topological surface states (TSS), such as Bi 2 Se 3 , (Bi,Sb)Te 3 , and BiSb, have demonstrated very high θ SH larger than 1 at room temperature in epitaxial TI thin films prepared by molecular beam epitaxy 9 – 11 . Moreover, the high θ SH is maintained even in non-epitaxial TIs prepared by the industry-friendly sputtering technique 12 – 15 . Thus, TIs are very promising for magnetization manipulation with ultralow power consumption, and considered as the second-generation of spin Hall materials.…”

Section: Introductionmentioning

confidence: 99%

Efficient spin current source using a half-Heusler alloy topological semimetal with back end of line compatibility

Shirokura

Fan

Khang

et al. 2022

Sci Rep

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Topological materials, such as topological insulators (TIs), have great potential for ultralow power spintronic devices, thanks to their giant spin Hall effect. However, the giant spin Hall angle (θSH > 1) is limited to a few chalcogenide TIs with toxic elements and low melting points, making them challenging for device integration during the silicon Back-End-of-Line (BEOL) process. Here, we show that by using a half-Heusler alloy topological semi-metal (HHA-TSM), YPtBi, it is possible to achieve both a giant θSH up to 4.1 and a high thermal budget up to 600 °C. We demonstrate magnetization switching of a CoPt thin film using the giant spin Hall effect of YPtBi by current densities lower than those of heavy metals by one order of magnitude. Since HHA-TSM includes a group of three-element topological materials with great flexibility, our work opens the door to the third-generation spin Hall materials with both high θSH and high compatibility with the BEOL process that would be easily adopted by the industry.

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“…Similarly, interfacial PMA magnetic layer and efficient SOT switching have been obtained in Bi x Te 1− x /Pt/Co/Pt, Bi 2 Se 3 /Co/Pt. [ 169 , 170 ]…”

Section: Spin‐orbit Torque‐induced Magnetization Switching With Low Critical Current Densitymentioning

confidence: 99%

Spin‐Orbit Torque in Van der Waals‐Layered Materials and Heterostructures

Tang

Liu

et al. 2021

Advanced Science

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Spin-orbit torque (SOT) opens an efficient and versatile avenue for the electrical manipulation of magnetization in spintronic devices. The enhancement of SOT efficiency and reduction of power consumption are key points for the implementation of high-performance SOT devices, which strongly rely on the spin-orbit coupling (SOC) strength and magnetic properties of ferromagnetic/non-magnetic heterostructures. Recently, van der Waals-layered materials have shown appealing properties for use in efficient SOT applications. On the one hand, transition-metal dichalcogenides, topological insulators, and graphene-based heterostructures possess appreciable SOC strength. This feature can efficiently converse the charge current into spin current and result in large SOT. On the other hand, the newly discovered layered magnetic materials provide ultra-thin and gate-tunable ferromagnetic candidates for high-performance SOT devices. In this review, the latest advancements of SOT research in various layered materials are summarized. First, a brief introduction of SOT is given. Second, SOT studies of various layered materials and heterostructures are summarized. Subsequently, progresses on SOT-induced magnetization switching are presented. Finally, current challenges and prospects for future development are suggested.

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Efficient Spin–Orbit Torque Switching with Nonepitaxial Chalcogenide Heterostructures

Cited by 33 publications

References 39 publications

Ultralow power spin–orbit torque magnetization switching induced by a non-epitaxial topological insulator on Si substrates

Ultralow power spin–orbit torque magnetization switching induced by a non-epitaxial topological insulator on Si substrates

Efficient spin current source using a half-Heusler alloy topological semimetal with back end of line compatibility

Spin‐Orbit Torque in Van der Waals‐Layered Materials and Heterostructures

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