Large-amplitude coherent spin waves excited by spin-polarized current in nanoscale spin valves

Berkov, D. V.; Gorn, N. L.; Emley, N. C.; Sankey, J. C.; Ralph, Daniel; Buhrman, R. A.

doi:10.1103/physrevb.76.024418

Cited by 104 publications

(129 citation statements)

References 76 publications

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“…6. As discussed in our previous work 39 , these jumps are caused by the transitions between modes with different spatial localization patterns. However, the mode localization pattern may change without leading to an appreciable frequency jump.…”

Section: B Effect Of the Py Exchange Constant A Pymentioning

confidence: 99%

“…As discussed in our Ref. [39], such a jump is due to transition between modes with different spatial localization patterns and as such should be sensitive to shape imperfections of the active layer. For this reason, we cannot expect the exact agreement of the simulated and measured frequencies for the jump locations.…”

Section: Comparison With Experimentsmentioning

confidence: 99%

“…For the spin torque we use the standard Slonczewski term as in our previous publications 37,39 . The spin torque magnitude is proportional to P·I, where P is the degree of spin polarization of the electrical current.…”

Section: A Simulation Detailsmentioning

confidence: 99%

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Micromagnetic simulations of magnetization dynamics in a nanowire induced by a spin-polarized current injected via a point contact

Berkov

Boone

2011

Phys. Rev. B

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We present a detailed numerical analysis of the magnetization auto-oscillations induced in a thin NiFe nanowire by a direct spin polarized current injected via a square-shaped CoFe nanomagnet (a system experimentally studied in C. Boone et al., Phys. Rev. B 79, 140404 (2009)). We demonstrate that all auto-oscillation modes in the nanowire are localized under the nanocontact for magnetic field applied in the plane of the nanowire. This mode localization is induced by a strong stray magnetic field acting on the NiFe nanowire from the CoFe current injector. We find that the auto-oscillation frequency, power and the frequency shift with the current strongly depend on the exchange constant of NiFe. We also find that the auto-oscillation power depends non-monotonically on the CoFe saturation magnetization, and demonstrate that this effect has its origin in resonant excitation of the CoFe eigenmodes by magnetization oscillations in the NiFe nanowire. The calculated dependence of the oscillation frequency on current is in a good agreement with the experiment. However, the agreement between theory and experiment for the oscillation power is unsatisfactory. Finally, we have shown that an auto-oscillatory mode propagating along the nanowire in the system under study is possible when a sufficiently strong out-of-plane field is applied.

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Section: B Effect Of the Py Exchange Constant A Pymentioning

confidence: 99%

Section: Comparison With Experimentsmentioning

confidence: 99%

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Micromagnetic simulations of magnetization dynamics in a nanowire induced by a spin-polarized current injected via a point contact

Berkov

Boone

2011

Phys. Rev. B

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“…1 Recent measurements of the dispersion and damping of spin-wave excitations driven by a direct spin-polarized current prove that the theoretical picture is incomplete, particularly when it comes to calculating the linewidth of these excitations. 2 One of the most important parameters of the theory is the so-called Gilbert damping parameter ␣, 3 which controls the damping rate and thermal noise and is often assumed to be independent of the wave vector of the excitations. This assumption is justified for excitations of very long wavelength ͑e.g., a homogeneous precession of the magnetization͒, where ␣ can originate in a relatively weak spin-orbit ͑SO͒ interaction.…”

Section: Introductionmentioning

confidence: 99%

Inhomogeneous Gilbert damping from impurities and electron-electron interactions

2008

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We present a unified theory of magnetic damping in itinerant electron ferromagnets at order q 2 including electron-electron interactions and disorder scattering. We show that the Gilbert damping coefficient can be expressed in terms of the spin conductivity, leading to a Matthiessen-type formula in which disorder and interaction contributions are additive. In a weak ferromagnet regime, electron-electron interactions lead to a strong enhancement of the Gilbert damping.

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“…This kind of mode splitting has been observed in experiments [61] and numerical studies based on a conventional micromagnetic model with no lateral spin torque [62,63]. Because of this mode splitting, the linewidth obtained from the fit using a single Lorentzian function increases rapidly with temperature.…”

Section: Spin Valvesmentioning

confidence: 80%

Self-consistent calculation of spin transport and magnetization dynamics

et al. 2013

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A spin-polarized current transfers its spin-angular momentum to a local magnetization, exciting various types of current-induced magnetization dynamics. So far, most studies in this field have focused on the direct effect of spin transport on magnetization dynamics, but ignored the feedback from the magnetization dynamics to the spin transport and back to the magnetization dynamics. Although the feedback is usually weak, there are situations when it can play an important role in the dynamics. In such situations, simultaneous, self-consistent calculations of the magnetization dynamics and the spin transport can accurately describe the feedback. This review describes in detail the feedback mechanisms, and presents recent progress in self-consistent calculations of the coupled dynamics. We pay special attention to three representative examples, where the feedback generates non-local effective interactions for the magnetization after the spin accumulation has been integrated out. Possibly the most dramatic feedback example is the dynamic instability in magnetic nanopillars with a single magnetic layer. This instability does not occur without non-local feedback. We demonstrate that full self-consistent calculations generate simulation results in much better agreement with experiments than previous calculations that addressed the feedback effect approximately.The next example is for more typical spin valve nanopillars. Although the effect of feedback is less dramatic because even without feedback the current can make stationary states unstable and induce magnetization oscillation, the feedback can still have important consequences. For instance, we show that the feedback can reduce the linewidth of oscillations, in agreement with experimental observations. A key aspect of this reduction is the suppression of the excitation of short wave length spin waves by the non-local feedback.Finally, we consider nonadiabatic electron transport in narrow domain walls. The non-local feedback in these systems leads to a significant renormalization of the effective nonadiabatic 3 spin transfer torque. These examples show that the self-consistent treatment of spin transport and magnetization dynamics is important for understanding the physics of the coupled dynamics and for providing a bridge between the ongoing research fields of current-induced magnetization dynamics and the newly emerging fields of magnetization-dynamics-induced generation of charge and spin currents.

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Large-amplitude coherent spin waves excited by spin-polarized current in nanoscale spin valves

Abstract: Abstract:We present spectral measurements of spin-wave excitations driven by direct spin-

Cited by 104 publications

References 76 publications

Micromagnetic simulations of magnetization dynamics in a nanowire induced by a spin-polarized current injected via a point contact

Micromagnetic simulations of magnetization dynamics in a nanowire induced by a spin-polarized current injected via a point contact

Inhomogeneous Gilbert damping from impurities and electron-electron interactions

Self-consistent calculation of spin transport and magnetization dynamics

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