Fast and efficient STT switching in MTJ using additional transient pulse current

Pathak, Sachin; Cha, Ji-Young; Jo, Kangwook; Yoon, Hongil; Hong, Jongill

doi:10.1063/1.4985129

Cited by 12 publications

(5 citation statements)

References 17 publications

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“…Various schemes are introduced to overcome these obstacles. For example, they are the application of a manipulated write pulse current and the use of voltage control magnetic anisotropy (VCMA) or spin-orbit torque (SOT) with the assisting STT [11][12][13][14] . All of these schemes are gaining great attention equally in recent times.…”

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confidence: 99%

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Impact of Spin-Orbit Torque on Spin-Transfer Torque Switching in Magnetic Tunnel Junctions

Pathak

Youm

Hong

2020

Sci Rep

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the paper presents our simulated results showing the substantial improvement of both switching speed and energy consumption in a perpendicular magnetic tunnel junction (p-MTJ), a core unit of Spin-Transfer-Torque Magnetic Random Access Memory (STT-MRAM), by the help of additional Spin-Orbit-Torque (SOT) write pulse current (WP Sot ). An STT-SOT hybrid torque module for OOMMF simulation is implemented to investigate the switching behavior of a 20 nm cell in the p-MTJ. We found that the assistance of WP Sot to STT write pulse current (WP Stt ) have a huge influence on the switching behavior of the free layer in the p-MTJ. For example, we could dramatically reduce the switching time (t SW ) by 80% and thereby reduce the write energy over 70% as compared to those in the absence of the WP Sot . Even a very tiny amplitude of WP Sot (J Sot of the order of 10 2 A/m 2 ) substantially assists to reduce the critical current density for switching of the free layer and thereby decreases the energy consumption as well. It is worth to be pointed out that the energy can be saved further by tuning the WP Sot parameters, i.e., amplitude and duration along at the threshold WP Stt . Our findings show that the proposed STT-SOT hybrid switching scheme has a great impact on the MRAM technology seeking the high speed and low energy consumption.Magnetic Random Access Memory (MRAM) has known to be an outstanding candidate among next-generation memories due to its various advantages, such as non-volatility, high-speed operation, high density and scalability, over other competing memories 1-4 . In particular, spin-transfer torque MRAM (STT-MRAM) composed of perpendicular magnetic tunnel junctions (p-MTJs) has received a significant attention because it offers reduced write current and strong thermal stability 5 . In an MTJ, there are two ferromagnetic (FM) layers separated by an insulating tunneling barrier. One FM layer has a fixed magnetization and another has a variable magnetization (called as a free layer) which can be made to align either parallel (P) or anti-parallel (AP) with respect to the fixed layer. Magnetization of the free layer is used to store the data and can be switched by spin-polarized electrons (equivalently spin current) without a magnetic field. When the spin-polarized current flows through the free layer, the layer absorbs spin angular momentum from the electrons and as a result, its magnetization flips, which is the reason why we call it spin (momentum) transfer torque. STT-MRAM faces various challenges along with its merits such as, the reliability of a tunnel barrier, long write latency and small energy efficiency due to still high write current. Out of these, the most important issue which needs to be counter first is high energy consumption due to high write current and long write latency. The current density for switching of STT-MRAM is relatively large and hence large transistors are inevitable to drive it, which thus significantly limits their future use for memory applications 6,7 . The sustainability of hig...

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confidence: 99%

“…All of these schemes are gaining great attention equally in recent times. In our previous study, we found a way to save the energy by using an overshoot transient pulse in the case of STT switching 12 . The energy could be saved up to 9%.…”

mentioning

confidence: 99%

Impact of Spin-Orbit Torque on Spin-Transfer Torque Switching in Magnetic Tunnel Junctions

Pathak

Youm

Hong

2020

Sci Rep

Self Cite

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“…4, we show how the charge current flowing through the MTJ varies with time. The peak current density is 6.5× 10 11 A/m 2 which is high, but not completely unreasonable since current densities of this order have been used in MTJs [6,14,15]. Reducing it would have required reducing the power supply voltage Vs.…”

Section: Resultsmentioning

confidence: 99%

Microwave Oscillator Based on a Single Straintronic Magnetotunneling Junction

2019

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There is growing interest in exploring nanomagnetic devices as potential replacements for electronic devices (e.g. transistors) in digital switching circuits and systems. A special class of nanomagnetic devices are switched with electrically generated mechanical strain leading to electrical control of magnetism. Straintronic magneto-tunneling junctions (s-MTJ) belong to this category. Their soft layers are composed of two-phase multiferroics comprising a magnetostrictive layer elastically coupled to a piezoelectric layer.Here, we show that a single straintronic magneto-tunneling junction with a passive resistor can act as a microwave oscillator whose traditional implementation would have required microwave operational amplifiers, capacitors and resistors. This reduces device footprint and cost, while improving device reliability. This is an analog application of magnetic devices where magnetic interactions (interaction between the shape anisotropy, strain anisotropy, dipolar coupling field and spin transfer torque in the soft layer of the s-MTJ) are exploited to implement an oscillator with reduced footprint. I.

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“…The roughness variation was incorporated to OOMMF based on the corresponding variation in damping constant. Here, the parameters of the free layer were optimized via atomistic simulation and the parameters of the fixed layer were based on the findings in [30]. The saturation magnetization assigned was 1.1 × 10 6 A m −1 and the spin-torque efficiency used is 0.7.…”

Section: Simulationmentioning

confidence: 99%

Interface imperfection effects on spin transfer torque switching: an atomistic approach

Ramesh¹,

Cheng²,

Ku³

et al. 2022

J. Phys. D: Appl. Phys.

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The further commercialization of spintronic memory devices depends on the development of methods by which to assess performance. This paper presents an approach to the atomistic investigation of switching performance in spin transfer torque (STT) magneto-resistive random access memory (MRAM) devices with the use of interface imperfection model. Switching simulation in the nanosecond regime was made possible under this model, and we first time demonstrate that switching time is inversely proportional to interface imperfection (i.e. roughness). In investigating the damping of CoFeB/MgO films, we analyzed the effective damping constant , which cannot be accurately predicted for ferromagnetic layers of less than 2 nm using existing micromagnetic models. The proposed model includes a roughness parameter, which has nearly no effect on the effective damping constant in films of >2nm, but a profound effect in films of <2nm, reaching a 27% decrease in a 1.0 nm CoFeB film. Our finding is supported by the experimental data of classic references. We expect that these results will prove valuable in magnetic simulation and research on MRAM with ultrathin films.

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Fast and efficient STT switching in MTJ using additional transient pulse current

Cited by 12 publications

References 17 publications

Impact of Spin-Orbit Torque on Spin-Transfer Torque Switching in Magnetic Tunnel Junctions

Impact of Spin-Orbit Torque on Spin-Transfer Torque Switching in Magnetic Tunnel Junctions

Microwave Oscillator Based on a Single Straintronic Magnetotunneling Junction

Interface imperfection effects on spin transfer torque switching: an atomistic approach

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