Theory of current-driven magnetization dynamics in inhomogeneous ferromagnets

Tserkovnyak, Yaroslav; Brataas, Arne; Bauer, G.

doi:10.1016/j.jmmm.2007.12.012

Cited by 138 publications

(150 citation statements)

References 89 publications

(253 reference statements)

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“…Therefore, we believe that the inclusion of a damping term proportional to q 2 in the phenomenological LandauLifshitz equation of motion for the magnetization 14 is a potentially important modification of the theory in strongly inhomogeneous situations, such as current-driven nanomagnets 2 and the ferromagnetic domain-wall motion. 15,16 …”

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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Section: Introductionmentioning

confidence: 99%

Inhomogeneous Gilbert damping from impurities and electron-electron interactions

2008

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“…Remedying the incomplete understanding of non-adiabatic spin torque is of particular relevance because in current driven dynamics it governs domain wall velocity, which scales linearly with β below the Walker breakdown limit, where the domain wall begins to experience turbulent motion and mobility is greatly affected [6][7][8] . Thus, the development of new spin torque devices will be facilitated by a more complete understanding of the non-adiabatic torque 9 .…”

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confidence: 99%

Direct dynamic imaging of non-adiabatic spin torque effects

et al. 2012

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spin-transfer torques offer great promise for the development of spin-based devices. The effects of spin-transfer torques are typically analysed in terms of adiabatic and non-adiabatic contributions. Currently, a comprehensive interpretation of the non-adiabatic term remains elusive, with suggestions that it may arise from universal effects related to dissipation processes in spin dynamics, while other studies indicate a strong influence from the symmetry of magnetization gradients. Here we show that enhanced magnetic imaging under dynamic excitation can be used to differentiate between non-adiabatic spin-torque and extraneous influences. We combine Lorentz microscopy with gigahertz excitations to map the orbit of a magnetic vortex core with < 5 nm resolution. Imaging of the gyrotropic motion reveals subtle changes in the ellipticity, amplitude and tilt of the orbit as the vortex is driven through resonance, providing a robust method to determine the non-adiabatic spin torque parameter β = 0.15 ± 0.02 with unprecedented precision, independent of external effects.

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“…It may also find use in storage and logic devices in which the domain wall is used as the information unit (for comprehensive reviews about current-induced domain wall motion based on local spin transfer torque, please see Refs. [83][84][85][86][87]). …”

Section: Current-induced Motion Of a Domain Wallmentioning

confidence: 99%

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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Theory of current-driven magnetization dynamics in inhomogeneous ferromagnets

Cited by 138 publications

References 89 publications

Inhomogeneous Gilbert damping from impurities and electron-electron interactions

Inhomogeneous Gilbert damping from impurities and electron-electron interactions

Direct dynamic imaging of non-adiabatic spin torque effects

Self-consistent calculation of spin transport and magnetization dynamics

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