Dual Referenced Composite Free Layer Design for Improved Switching Efficiency of Spin-Transfer Torque Random Access Memory

Bell, Roy; Hu, Jiaxi; Victora, R. H.

doi:10.1109/led.2016.2592324

Cited by 10 publications

(4 citation statements)

References 25 publications

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“…R P is the MTJ resistance when both magnets are exactly parallel (P) to each other and assumed to remain invariant to V MTJ for all practical purpose [46,49], while R AP0 is the MTJ resistance when both magnets are exactly anti-parallel (AP) to each other at a zero-bias. Since in the recent years Slonczewski expression [27] for spin-torque efficiency has been extended to account for multiple reflections of the spin-flux in the spin valves [50][51][52][53], the STT effect by the BL in this study is based on the multi-reflection model. Hence, the STT efficiencies for the PL-MgO-FL MTJ (η MTJ ) and the FL-Metal-BL spin valve (η SV ) are computed as [52,54],…”

Section: Methodsmentioning

confidence: 99%

Ultrafast and low-energy switching in voltage-controlled elliptical pMTJ

Deng

Liang

Gupta³

2017

Sci Rep

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Switching magnetization in a perpendicular magnetic tunnel junction (pMTJ) via voltage controlled magnetic anisotropy (VCMA) has shown the potential to markedly reduce switching energy. However, the requirement of an external magnetic field poses a critical bottleneck for its practical applications. In this work, we propose an elliptical-shaped pMTJ to eliminate the requirement of providing an external field by an additional circuit. We demonstrate that a 10 nm thick in-plane magnetized bias layer (BL) separated by a metallic spacer of 3 nm from the free layer (FL) can be engineered within the MTJ stack to provide the 50 mT bias magnetic field for switching. By conducting macrospin simulation, we find that a fast switching in 0.38 ns with energy consumption as low as 0.3 fJ at a voltage of 1.6 V can be achieved. Furthermore, we study the phase diagram of switching probability, showing that a pulse duration margin of 0.15 ns is obtained and low-voltage operation (~1 V) is favored. Finally, the MTJ scalability is considered, and it is found that scaling down may not be appealing in terms of both the energy consumption and the switching time for precession based VCMA switching.

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Section: Methodsmentioning

confidence: 99%

Ultrafast and low-energy switching in voltage-controlled elliptical pMTJ

Deng

Liang

Gupta³

2017

Sci Rep

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“…Yet, in this study, the highest efficiency is obtained for a double MTJ with higher RA B and low RA T (black square data). The possibility to achieve higher improvement factors has been in fact predicted for optimized material stacks. , …”

Section: Comparative Studymentioning

confidence: 99%

Spin Torque Efficiency Modulation in a Double-Barrier Magnetic Tunnel Junction with a Read/Write Mode Control Layer

Chavent

Coelho

Chatterjee

et al. 2021

ACS Appl. Electron. Mater.

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To improve the read/write margin in perpendicular spin transfer torque magnetic random access memory (STT-MRAM), a concept of the double-magnetic tunnel junction (MTJ) MRAM cell is proposed in which the STT efficiency can be changed between read and write modes. In conventional double-MTJ stacks, the storage layer magnetization is submitted to two additive STT contributions, one from the reference layer below the bottom tunnel barrier and the other from an additional polarizing layer above the top tunnel barrier. In the proposed stack, the magnetization of the top polarizing layer can be switched between the read and write mode by domain wall propagation or spin orbit torque. This allows us to maximize the STT on the storage layer during write and minimize it during read. The associated advantages are a lower write current, reduced read disturb, maximal magnetoresistance amplitude during read, and faster read thanks to larger read current. We report here the experimental demonstration of this concept on perpendicular double-MTJ stacks.

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“…1.a) have demonstrated an up to 6x increase in spin-torque switching efficiency (ξ = ∆E/I crit ). [1][2][3][4][5] For a desired thermal stability, the requisite switching current is significantly reduced. This is critical for devices that begin to scale to several nanometer dimensions where thermal stability issues are significant.…”

Section: Introductionmentioning

confidence: 99%

“…1.c assists the magnetization reversal of the hard layer via exchange coupling resulting in a 2x increase in ξ. The amalgamation of both structures yields the dual-referenced composite free layer architecture 5 of Fig. 1.d, which has demonstrated a 6x improvement in ξ over the conventional MTJ.…”

Section: Introductionmentioning

confidence: 99%

Dual referenced composite free layer design optimization for improving switching efficiency of spin-transfer torque RAM

Bell

Victora

2017

AIP Advances

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We present a detailed numerical analysis of switching efficiency for the recently proposed dual referenced composite free layer structure with respect to Gilbert damping. Low anisotropy assistive layers enable reduction of Gilbert damping and an increase of partial spin polarization within those low anisotropy layers—not feasible with single layer structures that require high anisotropy for thermal stability. When the damping of the soft layers is ultra-low, an efficiency (kBT/μA) of 8.1 is achieved for the composite structure with perpendicular anisotropy. This represents an improvement of 286% and 913% relative to the state-of-the-art dual-referenced and conventional STT-RAM cells, respectively. Results for structures with longitudinal anisotropy are also presented. A linear calculation of the STT polarization pre-factor is also described that captures all reflections.

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Dual Referenced Composite Free Layer Design for Improved Switching Efficiency of Spin-Transfer Torque Random Access Memory

Cited by 10 publications

References 25 publications

Ultrafast and low-energy switching in voltage-controlled elliptical pMTJ

Ultrafast and low-energy switching in voltage-controlled elliptical pMTJ

Spin Torque Efficiency Modulation in a Double-Barrier Magnetic Tunnel Junction with a Read/Write Mode Control Layer

Dual referenced composite free layer design optimization for improving switching efficiency of spin-transfer torque RAM

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