Dynamics of spin torque switching in all-perpendicular spin valve nanopillars

Liu, H.; Bedau, D.; Sun, J. Z.; Mangin, Stéphane; Fullerton, Eric E.; Katine, J. A.; Kent, Andrew D.

doi:10.1016/j.jmmm.2014.01.061

Cited by 100 publications

(89 citation statements)

References 32 publications

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“…Both effects are entirely of dynamical nature, and their influence on the phase boundaries can be theoretically described using the formalism developed in Ref. [16]. Renormalization of the effective dynamic time allows one to link dependence between the critical current, pulse width, and finite temperature.…”

Section: Macrospin Simulationsmentioning

confidence: 99%

Respective influence of in-plane and out-of-plane spin-transfer torques in magnetization switching of perpendicular magnetic tunnel junctions

et al. 2015

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International audienceThe relative contributions of in-plane (damping-like) and out-of-plane (field-like) spin-transfer torques (STT) in the magnetization switching of out-of-plane magnetized magnetic tunnel junctions (pMTJ) has been theoretically analyzed using the transformed Landau-Lifshitz-Gilbert (LLG) equation with the STT terms. It is demonstrated that in a pMTJ structure obeying macrospin dynamics, the out-of-plane torque influences the precession frequency, but it does not contribute significantly to the STT switching process (in particular to the switching time and switching current density), which is mostly determined by the in-plane STT contribution. This conclusion is confirmed by finite temperature and finite writing pulse macrospin simulations of the current field switching diagrams. It contrasts with the case of STT switching in in-plane magnetized magnetic tunnel junction (MTJ) in which the field-like term also influences the switching critical current. This theoretical analysis was successfully applied to the interpretation of voltage field STT switching diagrams experimentally measured on pMTJ pillars 36 nm in diameter, which exhibit macrospin behavior. The physical nonequivalence of Landau and Gilbert dissipation terms in the presence of STT-induced dynamics is also discussed

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Section: Macrospin Simulationsmentioning

confidence: 99%

Respective influence of in-plane and out-of-plane spin-transfer torques in magnetization switching of perpendicular magnetic tunnel junctions

et al. 2015

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“…The influence of thermal fluctuations leads to a strong dependence of the critical current on pulse length. Note that thermal activation can be included in a macrospin calculation [10,[25][26][27]. iii) for magnetic elements with dimensions large enough to accomodate a domain wall, the reversal process can be driven by domain nucleation and propagation further reducing the energy barrier.…”

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confidence: 99%

Time Resolved Measurements of the Switching Trajectory of Pt/Co Elements Induced by Spin-Orbit Torques

et al. 2017

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We report the experimental observation of spin-orbit torque induced switching of perpendicularly magnetized Pt/Co elements in a time resolved stroboscopic experiment based on high resolution Kerr microscopy. Magnetization dynamics is induced by injecting sub-nanosecond current pulses into the bilayer while simultaneously applying static in-plane magnetic bias fields. Highly reproducible homogeneous switching on time scales of several tens of nanoseconds is observed. Our findings can be corroborated using micromagnetic modelling only when including a field-like torque term as well as the Dzyaloshinskii-Moriya interaction mediated by finite temperature.Magnetization switching induced by spin-orbit torques (SOTs) generated by in plane (ip) current pulses in ferromagnet (FM)/heavy metal (HM) bilayers has attracted great attention in recent years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. A typical structure comprises a FM element with perpendicular magnetization structured on top of a HM conductor carrying the current. Technologically such a device has the advantage that the write current causing magnetization switching does not have to pass through a potential memory element itself thus avoiding its degradation [18]. Studying magnetization dynamics in such elements is of interest since the exact mechanisms enabling deterministic magnetization reversal remain to be disentangled. SOT driven magnetization reversal in HM/FM bilayers originates from a combination of effects which manifest themselves as field and damping like torques. These torques arise from bulk and interface effects such as the bulk spin Hall effect (SHE) or the interfacial inverse spin Galvanic effect (iSGE). Recent efforts have been dedicated to the understanding of the switching process induced by static or quasi-static currents [1,2,4,5,10,15,19]. However, the nature of the switching process itself is still under debate. Two possible scenarios exist: coherent rotation [4] or domain nucleation and propagation [2]. The critical current densities required for these distinct processes differ by orders of magnitude since for domain driven reversal a much smaller energy barrier needs to be overcome. It is believed that for devices much larger than one domain wall width, the quasi-static switching process is domain driven [2,5,9,15]. However, when reducing the size, it has been demonstrated recently that the switching process can be described by uniform motion [14]. By studying switching probabilities using short current pulses of variable width [3,6,7,14] reliable switching for applied pulse widths as short as 180 ps [6] has been demonstrated. In these experiments, switching dynamics is investigated indirectly by examining the final state long after the current pulse has been applied. To understand the speed and type of the SOT induced switching process in detail, temporal and spatial resolution is required which is met in this Letter using time resolved scanning magneto-optical Kerr micoscopy (TRMOKE).Here we measure the trajectory of...

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“…Pinna et al 13 reported that, in a system with uniaxial anisotropy, n = 2 is a much better fit to the data at long time scales than n = 1, and the crossover regime between deterministic and thermal effects could span very large switching timescales. However, Liu et al 14 used n = 1 following the effective temperature argument, while Thomas et al 15 argued that n = 1 provides a better fit to their experimental data than n = 2. Fitting experimental data with equations (3) and (4) using n = 1 or n = 2 leads to large discrepancies in the values of ∆ as discussed below.…”

Section: Resultsmentioning

confidence: 99%

Estimation of thermal stability factor and intrinsic switching current from switching distributions in spin-transfer-torque devices with out-of-plane magnetic anisotropy

Heindl

Chaudhry²,

Russek

2018

AIP Advances

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We performed macromagnetic simulations of switching statistics in spin-transfer-torque devices with out-of-plane magnetic anisotropy and thermal stability factors ranging from Δ = 21 to Δ = 279. We compared our results of the simulated switching probabilities in low-currents (read-disturb) and long-times (thermally activated) limits with the predictions of several existing models that predict the switching probability to be proportional to (1 − I/Ic0)n (Eq. 3), with exponent n varying from n = 1 to n = 2.2. We found that the best match to the simulated data in these two limits is obtained with values of n ≈ 1.76, when currents are limited to ∼ 0.6-0.8 Ic0.

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Dynamics of spin torque switching in all-perpendicular spin valve nanopillars

Cited by 100 publications

References 32 publications

Respective influence of in-plane and out-of-plane spin-transfer torques in magnetization switching of perpendicular magnetic tunnel junctions

Respective influence of in-plane and out-of-plane spin-transfer torques in magnetization switching of perpendicular magnetic tunnel junctions

Time Resolved Measurements of the Switching Trajectory of Pt/Co Elements Induced by Spin-Orbit Torques

Estimation of thermal stability factor and intrinsic switching current from switching distributions in spin-transfer-torque devices with out-of-plane magnetic anisotropy

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