Calculation of energy-barrier lowering by incoherent switching in spin-transfer torque magnetoresistive random-access memory

Munira, Kamaram; Visscher, P. B.

doi:10.1063/1.4908153

Cited by 28 publications

(39 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…3(e)]. Following the predictions of 17 we conjecture that the DW is nucleated from the edge when the single-domain state is destabilized [ Fig. 3(f)].…”

Section: A Assumptions For the Domain Wall Mediated Switchingmentioning

confidence: 91%

Time-resolved spin-torque switching in MgO-based perpendicularly magnetized tunnel junctions

et al. 2016

View full text Add to dashboard Cite

We study ns scale spin-torque-induced switching in perpendicularly magnetized tunnel junctions (pMTJ). Although the switching voltages match with the macrospin instability threshold, the electrical signatures of the reversal indicate the presence of domain walls in junctions of various sizes. In the antiparallel (AP) to parallel (P) switching, a nucleation phase is followed by an irreversible flow of a wall through the sample at an average velocity of 40 m/s with back and forth oscillation movements indicating a Walker propagation regime. A model with a single-wall locally responding to the spin-torque reproduces the essential dynamical signatures of the reversal. The P to AP transition has a complex dynamics with dynamical back-hopping whose probability increases with voltage. We attribute this back-hopping to the instability of the nominally fixed layers.The spin-transfer-torque (STT) manipulation of the magnetization is a cornerstone of modern spintronics. In magnetic tunnel junctions (MTJ), the interplay between magnetizationdependent transport properties 1,2 and the spin torques results in a rich variety of phenomena 3 . After the discovery of STT, it was soon realized 4,5 that the cylindrical symmetry of the magnetic properties in Perpendicular Magnetic Anisotropy (PMA) systems and the resilience to thermal fluctuations that the anisotropy provides would make PMA systems ideal playgrounds to explore STT-induced dynamics. However MTJs with relevant properties became available only a decade after 6 and relied on ultrathin systems where strong interfacial effects can be present 7 ; besides, efficient spin-torque generation requires complex embedding stacks 8,9 in which each additional layers can be a fluctuator strongly coupled to the layer of main interest in a non uniform 8,10 and non local 11 manner. As a consequence the STT-induced magnetization switching in PMA MTJ systems exhibits rich features 12,13 that deserve to be studied, especially as it opens opportunities in information technologies.In this letter, we report single-shot time-resolved measurements of ns-scale STT switching events in PMA MTJs. We detail the electrical signature of the switching and account for its main features using a simple formalism. After an observable nucleation, the reversal proceeds in a non uniform manner with the motion of a domain wall (DW) in a Walker regime; this comes together with intensified excitations in the nominally fixed layers that can result in dynamical back-hopping. This complex dynamics calls for a revisit of the models describing the stability of magnetization and its switching under STT in perpendicularly magnetized confined systems. Our findings are also important for the understanding of other spin torque devices like spin majority gates 14 where the degree of coherence of the magnetization -the occurrence or non occurrence of domain walls-is crucial. The paper is organized as follows. We first describe in detail the properties of the thin films from which the samples are fabricated (section I). The d...

show abstract

“…3(e)]. Following the predictions of 17 we conjecture that the DW is nucleated from the edge when the single-domain state is destabilized [ Fig. 3(f)].…”

Section: A Assumptions For the Domain Wall Mediated Switchingmentioning

confidence: 91%

Time-resolved spin-torque switching in MgO-based perpendicularly magnetized tunnel junctions

et al. 2016

View full text Add to dashboard Cite

show abstract

“…For example, ref. [63] suggests a global magnetostatic instability in STT switching in PMAs, where a non-coherent precessional mode starts to destabilize and diverge when the precession amplitude becomes large. Once destabilized, the entire magnet will eventually flip.…”

Section: Non-coherent Switchingmentioning

confidence: 99%

From materials to systems: a multiscale analysis of nanomagnetic switching

Xie

Ganguly

et al. 2017

J Comput Electron

View full text Add to dashboard Cite

With the increasing demand for low-power electronics, nanomagnetic devices have emerged as strong potential candidates to complement present day transistor technology. A variety of novel switching effects such as spin torque and giant spin Hall offer scalable ways to manipulate nano-sized magnets. However, the low intrinsic energy cost of switching spins is often compromised by the energy consumed in the overhead circuitry in creating the necessary switching fields. Scaling brings in added concerns such as the ability to distinguish states (readability) and to write information without spontaneous backflips (reliability). A viable device must ultimately navigate a complex multi-dimensional material and design space defined by volume, energy budget, speed and a target read-write-retention error. In this paper, we review the major challenges facing nanomagnetic devices and present a multi-scale computational framework to explore possible innovations at different levels (material, device, or circuit), along with a holistic understanding of their overall energydelay-reliability tradeoff.

show abstract

“…The second effect -the increased frequency spacing between the modes at small diameters -is the expected effect of the confinement of the spin waves and the resulting increase of the exchange contribution to the mode frequencies 17 . The eigenmodes of perpendicularly magnetized circular disks are well understood and can be described analytically in a semi-quantitative manner 21,[24][25][26][27][28] . The frequency spacing between the lowest frequency modes scales with γ 0 H J where H J = 2Ak 2 µ0M S is a generalized exchange field with A the exchange stiffness.…”

Section: B Spin-waves Within the Free Layermentioning

confidence: 99%

“…The area shaped in red is the positive halo that surrounds the main (negative) peak in d e(χxx) dω . where k is a generalized wavevector 21,26,28 . The additional exchange contributions act on m x and m y on equal footing, hence they maintain the circularity of the precession.…”

Section: Linewidth Beyond the Macrospin Approximationmentioning

confidence: 99%

Using rf voltage induced ferromagnetic resonance to study the spin-wave density of states and the Gilbert damping in perpendicularly magnetized disks

Devolder

2017

Phys. Rev. B

View full text Add to dashboard Cite

We study how the shape of the spinwave resonance lines in rf-voltage induced FMR can be used to extract the spin-wave density of states and the Gilbert damping within the precessing layer in nanoscale magnetic tunnel junctions that possess perpendicular magnetic anisotropy. We work with a field applied along the easy axis to preserve the cylindrical symmetry of the uniaxial perpendicularly magnetized systems. We first describe the experimental set-up to study the susceptibility contributions of the spin waves in the field-frequency space. We then identify experimentally the maximum device size above which the spinwaves confined in the free layer can no longer be studied in isolation as the linewidths of their discrete responses make them overlap into a continuous density of states. The rf-voltage induced signal is the sum of two voltages that have comparable magnitudes: a first voltage that originates from the linear transverse susceptibility and rectification by magneto-resistance and a second voltage that arises from the non-linear longitudinal susceptibility and the resultant time-averaged change of the exact micromagnetic configuration of the precessing layer. The transverse and longitudinal susceptibility signals have different dc bias dependences such that they can be separated by measuring how the device rectifies the rf voltage at different dc bias voltages. The transverse and longitudinal susceptibility signals have different lineshapes; their joint studies in both fixed field-variable frequency, or fixed frequency-variable field configurations can yield the Gilbert damping of the free layer of the device with a degree of confidence that compares well with standard ferromagnetic resonance. Our method is illustrated on FeCoB-based free layers in which the individual spin-waves can be sufficiently resolved only for disk diameters below 200 nm. The resonance line shapes on devices with 90 nm diameters are consistent with a Gilbert damping of 0.011. A single value of the damping factor accounts for the line shape of all the spin-waves that can be characterized. This damping of 0.011 exceeds the value of 0.008 measured on the unpatterned films, which indicates that device-level measurements are needed for a correct evaluation of dissipation.

show abstract

Calculation of energy-barrier lowering by incoherent switching in spin-transfer torque magnetoresistive random-access memory

Cited by 28 publications

References 14 publications

Time-resolved spin-torque switching in MgO-based perpendicularly magnetized tunnel junctions

Time-resolved spin-torque switching in MgO-based perpendicularly magnetized tunnel junctions

From materials to systems: a multiscale analysis of nanomagnetic switching

Using rf voltage induced ferromagnetic resonance to study the spin-wave density of states and the Gilbert damping in perpendicularly magnetized disks

Contact Info

Product

Resources

About