Time-Resolved Switching Characteristic in Magnetic Tunnel Junction with Spin Transfer Torque Write Scheme

Iga, F.; Yoshida, Y.; Ikeda, Shoji; Hanyu, Takahiro; Ohno, Hideo; Endoh, Tetsuo

doi:10.7567/jjap.51.02bm02

Cited by 16 publications

(3 citation statements)

References 12 publications

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“…Our results suggest that differences in the sidewall passivation could also contribute. Previous workers have shown that monodomain dots have a variable incubation time prior to rapid (approximately 1.5 ns) switching [45,46], and that the distribution of incubation times is greater for smaller sizes. The delay is attributed to the time needed to climb the energy barrier.…”

Section: Discussionmentioning

confidence: 96%

Magnetoresistance Dynamics in Superparamagnetic Co−Fe−B Nanodots

et al. 2020

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Individual disk-shaped Co-Fe-B nanodots are driven into a superparamagnetic state by a spin-transfer torque, and their time-dependent magnetoresistance fluctuations are measured as a function of current. A thin layer of oxidation at the edges has a dramatic effect on the magnetization dynamics. A combination of experimental results and atomistic spin simulations shows that pinning to oxide grains can reduce the likelihood that fluctuations lead to reversal, and can even change the easy-axis direction. Exchange-bias loop shifts and training effects are observed even at room temperature after brief exposure to small fields. The results have implications for studies of core-shell nanoparticles and small magnetic tunnel junctions and spin-torque oscillators.

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Section: Discussionmentioning

confidence: 96%

Magnetoresistance Dynamics in Superparamagnetic Co−Fe−B Nanodots

et al. 2020

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“…The process of MTJ write is a process of alignment of the magnetic orientation of the regions of the ferromagnetic layer. The total switching time of STT-RAM consists of the incubation time and the transit time [8]. The incubation time is defined as the time needed for the electrons to climb up the potential barrier in an MTJ, while the transit time denotes the time for the electrons to descend the potential barrier to the other state.…”

Section: A Stt-ram Write Processmentioning

confidence: 99%

Variation-Tolerant Write Completion Circuit for Variable-Energy Write STT-RAM Architecture

Park

Zheng

Erez

et al. 2016

IEEE Trans. VLSI Syst.

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In this paper, we demonstrate an energy-reduction strategy that overcomes the stochastic switching characteristics of the spin-torque-transfer magnetic-RAM (STT-RAM) write operation and propose a write completion circuit needed for it. In contrast to the traditional worst case approach, which fixes the write duration for all cells, the proposed write technique terminates the write pulse after a write process finishes by monitoring the state of a cell. Since the average write duration is far shorter than the worst case duration, the average write energy is significantly reduced by the proposed architecture. We developed a write completion circuit for state change detection and bitline termination, and evaluated it using a compact STT-RAM model targeting an implementation in a 16-nm technology node. We also developed a variationtolerant version of the design specifically suited for handling significant variation in process parameters for both FETs and magnetic tunnel junctions (MTJs), and the low value of tunnel magnetoresistance of practical MTJs. Analysis indicates that at the required write-error rate, the proposed architecture reduces write energy by 36%-97% compared with the conventional designs relying on the worst case approach.Index Terms-Memory, process variation, spin-torque-transfer magnetic RAM, variable-energy write. 1063-8210

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“…Switching time of STT magnetization reversal in p-MTJs can be divided into two periods, incubation time and transit time. 18) The period of incubation time is defined as the period from the pulse rising to the onset of switching. Transit time is defined as the period between the onset of switching and the end of switching.…”

Section: Introductionmentioning

confidence: 99%

Impact of sub-volume excitation on improving overdrive delay product of sub-40 nm perpendicular magnetic tunnel junctions in adiabatic regime and its beyond

Ohuchida

Ito²,

Endoh

2015

Jpn. J. Appl. Phys.

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In this paper, we introduced a new figure of merit, overdrive delay product P od which is defined as the product of overdrive factor (I/I c0 % 1) and delay of transit time, to evaluate power consumption and switching delay from the viewpoint of perpendicular magnetic tunnel junctions (p-MTJs) switching. The impact of sub-volume excitation on the dependence of overdrive delay product on the junction size and material parameters of p-MTJs in adiabatic regime were clarified. Two strategies to decrease the P od were proposed. The first strategy is scaling down the junction size free from sub-volume effect. A reduction more than 86% of P od of p-MTJ with exchange stiffness A ij = 19 pJ/m was realized by scaling down the junction size from 70 to 10 nm when I/I c0 % 1 = 0.5. The second strategy is to increase A ij to suppress the effect of sub-volume excitation. A 26% reduction of the overdrive delay product was realized by enlarging A ij from 10 to 31 pJ/m with annealing process in the p-MTJ with the diameter of 40 nm. These results indicate that p-MTJs of embedded magnetoresistive random access memory (MRAM) should be scaled down under 30 nm where no sub-volume effect occurs for high speed programing.

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Time-Resolved Switching Characteristic in Magnetic Tunnel Junction with Spin Transfer Torque Write Scheme

Cited by 16 publications

References 12 publications

Magnetoresistance Dynamics in Superparamagnetic Co−Fe−B Nanodots

Magnetoresistance Dynamics in Superparamagnetic Co−Fe−B Nanodots

Variation-Tolerant Write Completion Circuit for Variable-Energy Write STT-RAM Architecture

Impact of sub-volume excitation on improving overdrive delay product of sub-40 nm perpendicular magnetic tunnel junctions in adiabatic regime and its beyond

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