Fast Low-Current Spin-Orbit-Torque Switching of Magnetic Tunnel Junctions through Atomic Modifications of the Free-Layer Interfaces

Shi, Shengjie; Ou, Yongxi; Aradhya, Sriharsha V.; Ralph, Daniel; Buhrman, R. A.

doi:10.1103/physrevapplied.9.011002

Cited by 89 publications

(105 citation statements)

References 32 publications

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“…[18] As compared in Table I, the value of ξ ≈ 0.30 DL j is significantly higher than those previously obtained in W devices (ξ ≈ − 0.20 DL j ), [24] Pt devices (ξ ≈ 0.12 DL j ), [14] and Pt 0.85 Hf 0.15 devices (ξ ≈ 0.23 DL j ) [17] when the spin current attenuation by the Hf spacer layers (A ≤ 1) is taken into account (note that A was assumed to be unity in previous reports [14,15,17,23] when calculating ξ DL j ). [18] As compared in Table I, the value of ξ ≈ 0.30 DL j is significantly higher than those previously obtained in W devices (ξ ≈ − 0.20 DL j ), [24] Pt devices (ξ ≈ 0.12 DL j ), [14] and Pt 0.85 Hf 0.15 devices (ξ ≈ 0.23 DL j ) [17] when the spin current attenuation by the Hf spacer layers (A ≤ 1) is taken into account (note that A was assumed to be unity in previous reports [14,15,17,23] when calculating ξ DL j ).…”

Section: Direct Current Switchingmentioning

confidence: 60%

“…[15] Low value of 4πM eff reduces the critical current for antidamping switching. [15] Low value of 4πM eff reduces the critical current for antidamping switching.…”

Section: Energy-efficient Ultrafast Sot-mrams Based Onmentioning

confidence: 98%

“…An alternative, 3-terminal spin-orbit torque (SOT) MRAM [8,9] has the potential to mitigate these issues. [7,[14][15][16][17] SOT-MRAMs based on a spin Hall metal that combines a giant spin Hall ratio (θ SH ) with a relatively low resistivity (ρ xx ) can also have unlimited endurance due to the suppression of Joule heating induced bursting and migration of the write line [2] as well as low values of write impedance that is compatible with superconducting circuits in cryogenic computing systems. The nonvolatile SOT-MRAMs can have long data retention, zero standby power, and fast and reliable write.…”

Section: Energy-efficient Ultrafast Sot-mrams Based Onmentioning

confidence: 99%

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Energy‐Efficient Ultrafast SOT‐MRAMs Based on Low‐Resistivity Spin Hall Metal Au_0.25Pt_0.75

Zhu

Shi

et al. 2020

Adv Elect Materials

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As shown in Figure 1b-d, the SOT-MTJ devices were lithographically patterned from sputter-deposited multilayer stacks consisting of Si/SiO 2 /Ta 1/Au 0.25 Pt 0.75 5/Hf 0.5/ Fe 0.6 Co 0.2 B 0.2Many key electronic technologies (e.g., large-scale computing, machine learning, and superconducting electronics) require new memories that are at the same time fast, reliable, energy-efficient, and of low-impedance, which has remained a challenge. Nonvolatile magnetoresistive random access memories (MRAMs) driven by spin-orbit torques (SOTs) have promise to be faster and more energy-efficient than conventional semiconductor and spin-transfer-torque magnetic memories. It is reported that the spin Hall effect of low-resistivity Au 0.25 Pt 0.75 thin films enables ultrafast antidamping-torque switching of SOT-MRAM devices for current pulse widths as short as 200 ps. If combined with industrial-quality lithography and already-demonstrated interfacial engineering, an optimized MRAM cell based on Au 0.25 Pt 0.75 can have energy-efficient, ultrafast, and reliable switching, for example, a write energy of <1 fJ (<50 fJ) for write error rate of 50% (<10 −5 ) for 1 ns pulses. The antidamping torque switching of the Au 0.25 Pt 0.75 devices is ten times faster than expected from a rigid macrospin model, most likely because of the fast micromagnetics due to the enhanced nonuniformity within the free layer. The feasibility of Au 0.25 Pt 0.75 -based SOT-MRAMs as a candidate for ultrafast, reliable, energy-efficient, low-impedance, and unlimited-endurance memory is demonstrated.

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Section: Direct Current Switchingmentioning

confidence: 60%

“…[15] Low value of 4πM eff reduces the critical current for antidamping switching. [15] Low value of 4πM eff reduces the critical current for antidamping switching.…”

Section: Energy-efficient Ultrafast Sot-mrams Based Onmentioning

confidence: 98%

Section: Energy-efficient Ultrafast Sot-mrams Based Onmentioning

confidence: 99%

See 1 more Smart Citation

Energy‐Efficient Ultrafast SOT‐MRAMs Based on Low‐Resistivity Spin Hall Metal Au_0.25Pt_0.75

Zhu

Shi

et al. 2020

Adv Elect Materials

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“…1(a)). Meanwhile, a high ρxx of a spin Hall material (e.g., ρxx ≥ 200 μΩ cm in Ta [2], W [8,13,14], and topological insulators [15,16]) is problematic for applications that require a high endurance [17] and low device impedance (∝ρxx) [18]. For example, use of a large-ρxx spin Hall material (e.g., ρxx =200 -300 μΩ cm for W, see Fig.…”

Section: *Lz442@cornelledumentioning

confidence: 99%

Maximizing Spin-Orbit-Torque Efficiency of Pt/Ti Multilayers: Trade-Off Between Intrinsic Spin Hall Conductivity and Carrier Lifetime

Zhu

Buhrman

2019

Phys. Rev. Applied

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We report a comprehensive study of the maximization of the spin Hall ratio (θSH) in Pt thin films by the insertion of submonolayer layers of Ti to decrease carrier lifetime while minimizing the concurrent reduction in the spin Hall conductivity. We establish that the intrinsic spin Hall conductivity of Pt, while robust against the strain and the moderate interruption of crystal order caused by these insertions, begins to decrease rapidly at high resistivity level because of the shortening carrier lifetime. The unavoidable trade-off between the intrinsic spin Hall conductivity and carrier lifetime sets a practical upper bound of θSH ≥0.8 for heterogeneous materials where the crystalline Pt component is the source of the spin Hall effect and the resistivity is increased by shortening carrier lifetime. This work also establishes a very promising spin-Hall metal of [Pt 0.75 nm/Ti 0.2 nm]7/Pt 0.75 nm for energy-efficient, high-endurance spin-orbit torque technologies (e.g., memories, oscillators, and logic) due to its combination of a giant θSH ≈ 0.8, or equivalently a dampinglike spin torque efficiency per unit current density DL ≈ 0.35, with a relatively low resistivity (90 μΩ cm) and high suitability for practical technology integration.Spin Hall metals with strong dampinglike spin-orbit torque (SOT) efficiency per unit current density ( DL ) and relatively low resistivity (ρxx) are the key for developing practical spin-orbit torque technologies (e.g., memories, oscillators, and logic)[1-10] that require energy efficiency, high endurance, and low impedance [11,12]. For example, for a SOT-MRAM device with a spin Hall channel (with thickness dHM and resistivity ρxx)/FM free layer (with thickness t and resistivity ρFM), the write current is approximately Iwrite∝ (1+s) / DL , and the corresponding write energy is Pwrite ∝ [(1+s) / DL ] 2 ρxx, where s ≈ tρxx/dHMρFM is the ratio of the current shunting in the FM layer over the current flow in the spin Hall channel (see Fig. 1(a)). Meanwhile, a high ρxx of a spin Hall material (e.g., ρxx ≥ 200 μΩ cm in Ta [2], W [8,13,14], and topological insulators [15,16]) is problematic for applications that require a high endurance [17] and low device impedance (∝ρxx) [18]. For example, use of a large-ρxx spin Hall material (e.g., ρxx =200 -300 μΩ cm for W, see Fig. 1(b)) will limit the endurance of SOT devices via Joule-heating-induced bursting and migration of the write line [17] as well as result in a high write impedance that is difficult for superconducting circuits in a cryogenic computing system to accommodate [18]. It is therefore of great technological and fundamental importance to establish how, why, and to what limit the spin Hall ratio (θSH) and DL of a spin Hall metal with a giant spin Hall conductivity (σSH) and a relatively low ρxx can be enhanced in practice.Among the various spin Hall metals, Pt is particularly attractive for spin-torque technologies due to its low ρxx, the highest intrinsic σSH known for the simple technologically viable metals (> 1.6×10 6 (ℏ/2e) Ω ...

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“…[23][24][25] It is known that the in-plane magnetic tunnel junction (MTJ) device by a spin transfer torque does not need an external field but takes a relatively long time for the switch due to an incubation time. [28][29][30][31][32] This in-plane device offers various possibilities in application so that more intensive study is needed.In this work, we investigated the new aspect of in-plane SOT device depending on the amplitudes of damping-like torque, field-like torque, the Oersted field torque and demagnetization torque by a macro spin simulation. [28][29][30][31][32] This in-plane device offers various possibilities in application so that more intensive study is needed.…”

mentioning

confidence: 99%

Spin‐Orbit Torque Driven Magnetization Switching and Precession by Manipulating Thickness of CoFeB/W Heterostructures

Kim

Chun

Yoon

et al. 2020

Adv Elect Materials

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has been proposed to facilitate the electrical manipulation of magnetization switching for magnetic random access memory and magnetic logic devices by using these toques. [2][3][4][5][6] Moreover, an oscillation and precessional motion by SOT can be a candidate for various types of oscillators. [7][8][9] The spin Hall effect (SHE) and the Rashba-Edelstein interaction are expected to be the main mechanisms of the current-induced SOT, where the two main constituents are the damping-like torque and field-like torque. [10][11][12][13] In the SHE, a spin current is generated in a direction perpendicular to the applied longitudinal charge current flowing in a normal metal (NM) and accumulates spins between FM and NM layers, which exerts a damping-like torque to the magnetization in FM. [14,15] In the Rashba-Edelstein effect, which is caused by the broken space inversion symmetry at the interface, spin accumulation is generated in a direction transverse to the charge current direction in the film plane, which exerts a torque on the magnetization in a ferromagnet (FM). [16][17][18][19][20] In addition to the spin Hall and Rashba-Edelstein effects, the Oersted field generated by the current in a metallic film is an additional source of driving torque. [21,22] In a perpendicular magnetic anisotropy (PMA) structure, these torques generated from a nano-second electric pulse switch the magnetization by a domain wall motion. [23][24][25] It is known that the in-plane magnetic tunnel junction (MTJ) device by a spin transfer torque does not need an external field but takes a relatively long time for the switch due to an incubation time. [26,27] But, recently, researchers demonstrated an in-plane MTJ device by SOT showing a fast deterministic switching at a low current density. [28][29][30][31][32] This in-plane device offers various possibilities in application so that more intensive study is needed.In this work, we investigated the new aspect of in-plane SOT device depending on the amplitudes of damping-like torque, field-like torque, the Oersted field torque and demagnetization torque by a macro spin simulation. We found that the switching, oscillation, and precession could occur in the same heterostructure like W/CoFeB by using the change of the torque ratio with different NM and FM thicknesses. In addition, we constructed the dynamic map as a function of the efficiency of each torque. The expansion and the shrinkage of the switching region are reflected in the map depending on the current density.The switching of magnetization via spin-orbit torque has attracted much attention because of its fast switching and low power consumption. Numerous studies have focused on increasing the conversion efficiency from charge to spin current and out-of-plane magnetization cases. Recently, there have been reports on the fast and deterministic switching of in-plane magnetization devices. It is reported that an in-plane spin-orbit torque (SOT) device can archive the oscillation, precession, and direct switching by a combination of torques-c...

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Fast Low-Current Spin-Orbit-Torque Switching of Magnetic Tunnel Junctions through Atomic Modifications of the Free-Layer Interfaces

Cited by 89 publications

References 32 publications

Energy‐Efficient Ultrafast SOT‐MRAMs Based on Low‐Resistivity Spin Hall Metal Au_0.25Pt_0.75

Energy‐Efficient Ultrafast SOT‐MRAMs Based on Low‐Resistivity Spin Hall Metal Au_0.25Pt_0.75

Maximizing Spin-Orbit-Torque Efficiency of Pt/Ti Multilayers: Trade-Off Between Intrinsic Spin Hall Conductivity and Carrier Lifetime

Spin‐Orbit Torque Driven Magnetization Switching and Precession by Manipulating Thickness of CoFeB/W Heterostructures

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Fast Low-Current Spin-Orbit-Torque Switching of Magnetic Tunnel Junctions through Atomic Modifications of the Free-Layer Interfaces

Cited by 89 publications

References 32 publications

Energy‐Efficient Ultrafast SOT‐MRAMs Based on Low‐Resistivity Spin Hall Metal Au0.25Pt0.75

Energy‐Efficient Ultrafast SOT‐MRAMs Based on Low‐Resistivity Spin Hall Metal Au0.25Pt0.75

Maximizing Spin-Orbit-Torque Efficiency of Pt/Ti Multilayers: Trade-Off Between Intrinsic Spin Hall Conductivity and Carrier Lifetime

Spin‐Orbit Torque Driven Magnetization Switching and Precession by Manipulating Thickness of CoFeB/W Heterostructures

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Product

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Energy‐Efficient Ultrafast SOT‐MRAMs Based on Low‐Resistivity Spin Hall Metal Au_0.25Pt_0.75

Energy‐Efficient Ultrafast SOT‐MRAMs Based on Low‐Resistivity Spin Hall Metal Au_0.25Pt_0.75