Metastable Vortex State of Perpendicular Magnetic Anisotropy Free Layer in Spin Transfer Torque Magnetic Tunneling Junctions

You, Chun‐Yeol; Kim, Hyungsuk

doi:10.4283/jmag.2013.18.4.380

Cited by 9 publications

(6 citation statements)

References 15 publications

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“…Below this value, the magnetization adopts a vortex configuration. This confirms results which have been reported before [172]. For egg-shaped structure, we note that a K at 0.9 MJ/m 3 , the magnetization adopts an opposite out-of-plane configuration.…”

Section: Magnetocrystalline Anisotropy Investigationssupporting

confidence: 92%

“…For circular shaped MTJ the SAF stabilizes a third state between out-of-plane and in-plane configuration. This state is called vortex state which forms a circular in-plane magnetization around a center with out-of-plane magnetization consistent with previous simulations [172]. The SAF layer prevents the circular FL to fully turn in-plane.…”

Section: Magnetocrystalline Anisotropy Investigationssupporting

confidence: 84%

“…Due to the out-of-plane anisotropy in pMTJ, the shape effect is considered negligible. You and Kim have shown that the pMTJ stack with circular shape exhibit a stable out-of-plane vortex configuration, which is an intermediate state between in-plane and out-of-plane magnetization state [172]. The effect of the in-plane demagnetizing tensor on the reversal process of pMTJ has not been reported to our knowledge.…”

Section: C2 Motivationmentioning

confidence: 88%

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Current-induced spin-orbit torque effective fields in multilayer structures with perpendicular magnetic anisotropy

Engel¹

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Section: Magnetocrystalline Anisotropy Investigationssupporting

confidence: 92%

Section: Magnetocrystalline Anisotropy Investigationssupporting

confidence: 84%

Section: C2 Motivationmentioning

confidence: 88%

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Current-induced spin-orbit torque effective fields in multilayer structures with perpendicular magnetic anisotropy

Engel¹

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“…The variation tendencies of the magnetization for the final stable state with the increase of K u for the initially AP and P states are almost symmetric, but the absolute value of magnetization for the initially AP state is larger than that of P owing to the opposing characteristics of the stray field from the polarizer. Considering that the stable state of spin configuration is determined by the trade-off of inner energy, [23] the stable state of the free layer after switching for the initial P-state is the same as that after relaxation for the initial AP-state. Thus, we can explain the mechanism of vortex generation by analyzing the relaxation process for the corresponding initial state.…”

Section: Resultsmentioning

confidence: 99%

Dependence of switching process on the perpendicular magnetic anisotropy constant in P-MTJ

2018

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We investigate the dependence of the switching process on the perpendicular magnetic anisotropy (PMA) constant in perpendicular spin transfer torque magnetic tunnel junctions (P-MTJs) using micromagnetic simulations. It is found that the final stable states of the magnetization distribution of the free layer after switching can be divided into three different states based on different PMA constants: vortex, uniform, and steady. Different magnetic states can be attributed to a trade-off among demagnetization, exchange, and PMA energies. The generation of the vortex state is also related to the non-uniform stray field from the polarizer, and the final stable magnetization is sensitive to the PMA constant. The vortex and uniform states have different switching processes, and the switching time of the vortex state is longer than that of the uniform state due to hindrance by the vortex.

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“…But with an increasing cross-sectional area of the device, the mechanism of FL switching becomes complicated due to domain formation, making it difficult to have an empirical expression for ∆ computation. The desired value of ∆ depends upon the allowable chip failure rate and for practical applications it is expected to be greater than 60 [8], which has been difficult to achieve in nanomagnets that rely on bulk anisotropy. With the proper reduction of the thickness of the FL, the interface anisotropy term dominates resulting in perpendicular magnetic anisotropy (PMA) MTJ with ∆ increased above 60 [9].…”

Section: Introductionmentioning

confidence: 99%

Cross-Sectional Area Dependence of Tunnel Magnetoresistance, Thermal Stability, and Critical Current Density in MTJ

Lone

Shringi

et al. 2021

IEEE Trans. Magn.

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Tunnel magneto-resistance (TMR), thermal stability, and critical switching current are important metrics of a magnetic tunnel junction (MTJ). In this work, a detailed study of these metrics is conducted for the down-scaling of the transverse dimensions of the MTJ. The quantum transport and the magnetization dynamics simulations are performed using nonequilibrium Green's function in the mode-space approach and Object Oriented Micromagnetic Framework (OOMMF), respectively. The study of areal size quantization effects on the TMR shows that most of the contribution to the TMR comes from lower energy sub-bands and that the TMR saturates for dimensions above 50 nm. An anomalous behavior is observed in the bias dependence of TMR for the lower energy sub-bands and is explained in terms of the modified Slonczewski's analytical model for conductance around zero bias. The study of TMR scaling is extended to consider non-idealities by introducing elastic dephasing into our simulations. It is shown that with down-scaling of diameters, dephasing affects the zero bias TMR predominantly below 20 nm. Further, TMR is also studied in terms of sensitivity to the variations in the interface layer and the asymmetric reduction of TMR with bias and its reversal at higher bias is observed. OOMMF simulations of the larger stack, including the free layer, are carried out to understand the qualitative link between magnet switching behavior, thermal stability, and critical current density with area scaling. It is shown that the area dependence of thermal stability and critical current follow each other qualitatively and the scaling of both these metrics is correlated to different regimes of magnetization switching such as macrospin behavior or formation of metastable complex textures. The implications of scaling, on the various MTJ metrics, are discussed in terms of the application domain.

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Metastable Vortex State of Perpendicular Magnetic Anisotropy Free Layer in Spin Transfer Torque Magnetic Tunneling Junctions

Cited by 9 publications

References 15 publications

Current-induced spin-orbit torque effective fields in multilayer structures with perpendicular magnetic anisotropy

Current-induced spin-orbit torque effective fields in multilayer structures with perpendicular magnetic anisotropy

Dependence of switching process on the perpendicular magnetic anisotropy constant in P-MTJ

Cross-Sectional Area Dependence of Tunnel Magnetoresistance, Thermal Stability, and Critical Current Density in MTJ

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