Spin-torque switching mechanisms of perpendicular magnetic tunnel junction nanopillars

Mohammadi, Jamileh Beik; Kent, Andrew D.

doi:10.1063/5.0046596

Cited by 8 publications

(4 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The introduction of terms of different symmetry and implicit dependence on the Gilbert damping is a non-obvious consequence of moving from the implicit LLGS equation to explicit form and often not discussed when performing numerical simulations [19][20][21][22], despite numerical packages solving the explicit form [7,8]. This complexity contributes to the confusion in the literature and also difficulty when interpreting experimental measurements between materials with different Gilbert damping constants.…”

Section: Theorymentioning

confidence: 99%

Spin-transfer and spin-orbit torques in the Landau–Lifshitz–Gilbert equation

Meo

Cronshaw²,

Jenkins³

et al. 2022

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

Dynamic simulations of spin-transfer and spin-orbit torques are increasingly important for a wide range of spintronic devices including magnetic random access memory, spin-torque nano-oscillators and electrical switching of antiferromagnets. Here we present a computationally efﬁcient method for the implementation of spin-transfer and spin-orbit torques within the Landau-Lifshitz-Gilbert equation used in micromagnetic and atomistic simulations. We consolidate and simplify the varying terminology of different kinds of torques into a physical action and physical origin that clearly shows the common action of spin torques while separating their different physical origins. Our formalism introduces the spin torque as an effective magnetic ﬁeld, greatly simplifying the numerical implementation and aiding the interpretation of results. The strength of the effective spin torque ﬁeld uniﬁes the action of the spin torque and subsumes the details of experimental effects such as interface resistance and spin Hall angle into a simple transferable number between numerical simulations. We present a series of numerical tests demonstrating the mechanics of generalised spin torques in a range of spin-tronic devices. This revised approach to modelling spin-torque effects in numerical simulations enables faster simulations and a more direct way of interpreting the results, and thus it is also suitable to be used in direct comparisons with experimental measurements or in a modelling tool that takes experimental values as input.

show abstract

Section: Theorymentioning

confidence: 99%

Spin-transfer and spin-orbit torques in the Landau–Lifshitz–Gilbert equation

Meo

Cronshaw²,

Jenkins³

et al. 2022

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

show abstract

“…While the threshold voltage and current increase relative to the case of perpendicularly magnetized layers, the impact on the overall switching-current requirement for a given write speed and write-error-rate, however, could be less significant. This is because to obtain very low switching errors, a fast write requires a spin current that is much larger than the instability threshold, and the switching dynamics can exhibit non-macrospin behavior [35][36][37][38][39] (e.g. non-uniform magnetization reversal and micromagnetic instabilities) that can modify the difference an increase in instability threshold makes to the overall memory cell optimization.…”

Section: B Switching Currentmentioning

confidence: 99%

A Perspective on Electrical Generation of Spin Current for Magnetic Random Access Memories

Safranski,

Sun,

Kent

2022

Preprint

View full text Add to dashboard Cite

Spin currents are used to write information in magnetic random access memory (MRAM) devices by switching the magnetization direction of one of the ferromagnetic electrodes of a magnetic tunnel junction (MTJ) nanopillar. Different physical mechanisms of conversion of charge current to spin current can be used in 2-terminal and 3-terminal device geometries. In 2-terminal devices, charge-to-spin conversion occurs by spin filtering in the MTJ's ferromagnetic electrodes and present day MRAM devices operate near the theoretically expected maximum charge-to-spin conversion efficiency. In 3-terminal devices, spin-orbit interactions in a channel material can also be used to generate large spin currents. In this perspective article, we discuss charge-to-spin conversion processes that can satisfy the requirements of MRAM technology. We emphasize the need to develop channel materials with larger charge-to-spin conversion efficiency-that can equal or exceed that produced by spin filtering-and spin currents with a spin polarization component perpendicular to the channel interface. This would enable high-performance devices based on sub-20 nm diameter perpendicularly magnetized MTJ nanopillars without need of a symmetry breaking field. We also discuss MRAM characteristics essential for CMOS integration. Finally, we identify critical research needs for charge-to-spin conversion measurements and metrics that can be used to optimize device channel materials and interface properties prior to full MTJ nanopillar device fabrication and characterization.

show abstract

“…Although the switching can be described theoretically by macrospin models [9 and 10], the magnetization reversal caused by STT and SOT is in general a complex and non-uniform process that involves the nucleation and expansion of magnetic domains [11 and 12]. This mechanism prevails over the pure macrospin dynamics even in devices as small as few tens of nm because it is more energetically favorable than the coherent rotation of all the magnetic moments [13][14][15][16]. Time-resolved measurements in magnetic tunnel junctions [16][17][18][19][20] and Hall crosses [21] have revealed that the non-uniform switching comprises two phases at the ns and sub-ns timescale: an initial waiting time t 0 during which the magnetization is at rest and the actual transition of duration ∆t.…”

Section: Introductionmentioning

confidence: 99%

Deterministic and stochastic aspects of current-induced magnetization reversal in perpendicular nanomagnets

et al. 2023

View full text Add to dashboard Cite

We study the incubation and transition times that characterize the magnetization switching induced by spin-orbit torques in nanomagnets with perpendicular anisotropy. We present a phenomenological model to interpret the dependence of the incubation time on the amplitude of the voltage pulse and assisting magnetic field, and estimate the volume of the seed domain that triggers the switching. Our measurements evidence a correlation between the incubation and transition times that is mediated by the temperature variation during the electric pulse. In addition, we discuss the stochastic distributions of the two times in terms of the energy barriers opposing the nucleation and expansion of the seed domain. We propose two models based on the log-normal and gamma functions to account for the different origin of the variability of the incubation and transition times, which are associated with a single nucleation barrier and multiple pinning sites, respectively.

show abstract

Spin-torque switching mechanisms of perpendicular magnetic tunnel junction nanopillars

Cited by 8 publications

References 26 publications

Spin-transfer and spin-orbit torques in the Landau–Lifshitz–Gilbert equation

Spin-transfer and spin-orbit torques in the Landau–Lifshitz–Gilbert equation

A Perspective on Electrical Generation of Spin Current for Magnetic Random Access Memories

Deterministic and stochastic aspects of current-induced magnetization reversal in perpendicular nanomagnets

Contact Info

Product

Resources

About