Thermal stability for domain wall mediated magnetization reversal in perpendicular STT MRAM cells with W insertion layers

Mihajlovic, G.; Smith, N.; Santos, T.; Li, J.; Terris, B. D.; Katine, J. A.

doi:10.48550/arxiv.2008.00412

Cited by 2 publications

(2 citation statements)

References 14 publications

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“…Because the reversal mechanism for the FL magnetization in devices with diameters larger than 50 nm that we have studied here is by do-main wall nucleation and propagation, 13,14 P (H) was fit using a domain wall reversal model. 12 An example of the fit is shown as black lines in Fig. 3b.…”

Section: Experimental Methodsmentioning

confidence: 99%

Ultrathin perpendicular free layers for lowering the switching current in STT-MRAM

Santos,

Mihajlovic,

Smith

et al. 2020

Preprint

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The critical current density J c0 required for switching the magnetization of the free layer (FL) in a spintransfer torque magnetic random access memory (STT-MRAM) cell is proportional to the product of the damping parameter, saturation magnetization and thickness of the free layer, αM S t F . Conventional FLs have the structure CoFeB/nonmagnetic spacer/CoFeB. By reducing the spacer thickness, W in our case, and also splitting the single W layer into two layers of sub-monolayer thickness, we have reduced t F while minimizing α and maximizing M S , ultimately leading to lower J c0 while maintaining high thermal stability. Bottom-pinned MRAM cells with device diameter in the range of 55-130 nm were fabricated, and J c0 is lowest for the thinnest (1.2 nm) FLs, down to 4 MA/cm 2 for 65 nm devices, ∼30% lower than 1.7 nm FLs. The thermal stability factor ∆ dw , as high as 150 for the smallest device size, was determined using a domain wall reversal model from field switching probability measurements. With high ∆ dw and lowest J c0 , the thinnest FLs have the highest spin-transfer torque efficiency.

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Section: Experimental Methodsmentioning

confidence: 99%

Ultrathin perpendicular free layers for lowering the switching current in STT-MRAM

Santos,

Mihajlovic,

Smith

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…Current flow through the junction leads to spin-transfer torques on the free layer magnetization that can switch it between magnetic states. In the macrospin limit-where the switching between these states is by coherent spin rotation-there are analytic models that characterize the thermally activated switching 14,20,21 and spin-transfer driven switching 5,22,23 .…”

Section: Introductionmentioning

confidence: 99%

Micromagnetic instabilities in spin-transfer switching of perpendicular magnetic tunnel junctions

Statuto,

Mohammadi,

Kent

2020

Preprint

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Micromagnetic instabilities and non-uniform magnetization states play a significant role in spin transfer induced switching of nanometer scale magnetic elements. Here we model domain wall mediated switching dynamics in perpendicularly magnetized magnetic tunnel junction nanopillars. We show that domain wall surface tension always leads to magnetization oscillations and instabilities associated with the disk shape of the junction. A collective coordinate model is developed that captures aspects of these instabilities and illustrates their physical origin. Model results are compared to those of micromagnetic simulations. The switching dynamics is found to be very sensitive to the domain wall position and phase, which characterizes the angle of the magnetization in the disk plane. This sensitivity is reduced in the presence of spin torques and the spin current needed to displace a domain wall can be far less than the threshold current for switching from a uniformly magnetized state. A prediction of this model is conductance oscillations of increasing frequency during the switching process.

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Thermal stability for domain wall mediated magnetization reversal in perpendicular STT MRAM cells with W insertion layers

Cited by 2 publications

References 14 publications

Ultrathin perpendicular free layers for lowering the switching current in STT-MRAM

Ultrathin perpendicular free layers for lowering the switching current in STT-MRAM

Micromagnetic instabilities in spin-transfer switching of perpendicular magnetic tunnel junctions

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