Instant-On Spin Torque in Noncollinear Magnetic Tunnel Junctions

Bultynck, Olivier; Manfrini, Mauricio; Vaysset, Adrien; Swerts, Johan; Wilson, Christopher J.; Sorée, Bart; Heyns, Marc; Mocuta, D.; Radu, Iuliana; Devolder, T.

doi:10.1103/physrevapplied.10.054028

Cited by 17 publications

(17 citation statements)

References 49 publications

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“…While the incubation delays are still distributed for a diameter of 40 nm, the transition regimes exhibit very little variance and the distribution of transition times is particularly narrow: the magic diameter ensures a repeatable wall motion independent from the tilt dynamics and immune from its fluctuations. If implemented jointly with the strategies ensuring reliable nucleation [23][24][25][26] or/and reproducible wall tilt and wall position [27], this strategy opens the route for reproducible switching times, which is of interest for memory applications in which write error rates could be substantially lowered.…”

Section: Reproducibility Of the Transition Time And Conclusionmentioning

confidence: 99%

“…We conclude that the magic diameter ensures a repeatable wall motion independent from the tilt dynamics and immune from its fluctuations. If implemented jointly with the strategies ensuring reliable nucleation [22][23][24][25], this strategy opens the route for reproducible switching times, which is of interest for memory applications in which write error rates could be substantially lowered.…”

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confidence: 99%

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Stochastic Processes in Magnetization Reversal Involving Domain-Wall Motion in Magnetic Memory Elements

et al. 2021

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We show experimentally through single-shot time-resolved conductance measurements that magnetization reversal through domain wall motion in sub-100 nm diameter magnetic tunnel junctions is dominated by two distinct stochastic effects. The first involves the incubation delay related to domain wall nucleation, while the second results from stochastic motion in the Walker regime. Micromagnetics simulations reveal several contributions to temporal pinning of the wall near the disc center, including vertical Bloch line nucleation and wall precession. We show that a reproducible ballistic motion is recovered when Bloch and Néel wall profiles become degenerate in energy in optimally sized discs, which enables quasi-deterministic motion.

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Section: Reproducibility Of the Transition Time And Conclusionmentioning

confidence: 99%

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confidence: 99%

Stochastic Processes in Magnetization Reversal Involving Domain-Wall Motion in Magnetic Memory Elements

et al. 2021

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“…Over the years, different generations of PMA-MTJ stacks of been studied: some showed clear BH [9,10,13], some others did not [14][15][16][17]. Since our objective is to understand the phenomenon of BH, we have selected the MTJ stacks where BH is clearly happening.…”

Section: Samples and Methodsmentioning

confidence: 99%

Back hopping in spin transfer torque switching of perpendicularly magnetized tunnel junctions

et al. 2020

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We analyze the phenomenon of back hopping in spin-torque induced switching of the magnetization in perpendicularly magnetized tunnel junctions. The analysis is based on single-shot time-resolved conductance measurements of the pulse-induced back hopping. Studying several material variants reveals that the back hopping is a feature of the nominally fixed system of the tunnel junction. The back hopping is found to proceed by two sequential switching events that lead to a final state P of conductance close to-but distinct from-that of the conventional parallel state. The P state does not exist at remanence. It generally relaxes to the conventional antiparallel state if the current is removed. The P state involves a switching of the sole spin-polarizing part of the fixed layers. The analysis of literature indicates that back hopping occurs only when the spin-polarizing layer is too weakly coupled to the rest of the fixed system, which justifies a posteriori the mitigation strategies of back hopping that were implemented empirically in spin-transfer-torque magnetic random access memories.

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“…At 500 mV, i.e. a couple of dBs above the quasi-static switching threshold (400 mV), the switching proceeds in the usual [15,26,27] two steps [Fig. 1(a)].…”

Section: B Dynamics In Rectangular Elongated Devicesmentioning

confidence: 99%

Spin-torque induced wall motion in perpendicularly magnetized discs: ballistic versus oscillatory behavior

Bouquin,

Kim,

Bultynck

et al. 2021

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We use time-resolved measurement and modeling to study the spin-torque induced motion of a domain wall in perpendicular anisotropy magnets. In disc of diameters between 70 and 100 nm, the wall drifts across the disc with pronounced back-and-forth oscillations that arise because the wall moves in the Walker regime. Several switching paths occur stochastically and lead to distinct switching durations. The wall can cross the disc center either in a ballistic manner or with variably marked oscillations before and after the crossing. The crossing of the center can even occur multiple times if a vertical Bloch line nucleates within the wall. The wall motion is analyzed using a collective coordinate model parametrized by the wall position q and the tilt φ of its in-plane magnetization projection. The dynamics results from the stretch field, which describes the affinity of the wall to reduce its length and the wall stiffness field describing the wall tendency to reduce dipolar energy by rotating its tilt. The wall oscillations result from the continuous exchange of energy between to the two degrees of freedom q and φ. The stochasticity of the wall dynamics can be understood from the concept of the retention pond: a region in the q − φ space in which walls are transiently bound to the disc center. Walls having trajectories close to the pond must circumvent it and therefore have longer propagation times. The retention pond disappears for a disc diameter of typically 40 nm: the wall then moves in a ballistic manner irrespective of the dynamics of its tilt. The propagation time is then robust against fluctuations hence reproducible.

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Instant-On Spin Torque in Noncollinear Magnetic Tunnel Junctions

Cited by 17 publications

References 49 publications

Stochastic Processes in Magnetization Reversal Involving Domain-Wall Motion in Magnetic Memory Elements

Stochastic Processes in Magnetization Reversal Involving Domain-Wall Motion in Magnetic Memory Elements

Back hopping in spin transfer torque switching of perpendicularly magnetized tunnel junctions

Spin-torque induced wall motion in perpendicularly magnetized discs: ballistic versus oscillatory behavior

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