Excitations of incoherent spin-waves due to spin-transfer torque

Lee, Kyung Jin; Deac, A.; Redon, O.; Nozières, J. P.; Diény, B.

doi:10.1038/nmat1237

Cited by 241 publications

(196 citation statements)

References 17 publications

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“…In this connection we note, that although the frequencies for a quasichaotic regime are not given in Ref. 30, the transition scenario from a regular to a quasichaotic precession shown in Fig. 3c from Ref.…”

Section: A Comparison With Numerical Simulation Results Of Other Groupsmentioning

confidence: 84%

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Magnetization precession due to a spin-polarized current in a thin nanoelement: Numerical simulation study

Berkov

Gorn

2005

Phys. Rev. B

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In this paper a detailed numerical study (in frames of the Slonczewski formalism) of magnetization oscillations driven by a spin-polarized current through a thin elliptical nanoelement is presented. We show that a sophisticated micromagnetic model, where a polycrystalline structure of a nanoelement is taken into account, can explain qualitatively all most important features of the magnetization oscillation spectra recently observed experimentally (S.I. Kiselev et al., Nature, 425, 380 (2003)), namely: existence of several equidistant spectral bands, sharp onset and abrupt disappearance of magnetization oscillations with increasing current, absence of the out-of-plane regime predicted by a macrospin model and the relation between frequencies of so called small-angle and quasichaotic oscillations. However, a quantitative agreement with experimental results (especially concerning the frequency of quasichaotic oscillations) could not be achieved in the region of reasonable parameter values, indicating that further model refinement is necessary for a complete understanding of the spin-driven magnetization precession even in this relatively simple experimental situation.

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Section: A Comparison With Numerical Simulation Results Of Other Groupsmentioning

confidence: 84%

“…In addition, in several short reports 29,30 some qualitative aspects of the magnetization dynamics of elliptical nanoelements (concerning mainly the transition from a homogeneous to a non-coherent magnetization precession) were discussed.…”

Section: )mentioning

confidence: 99%

Magnetization precession due to a spin-polarized current in a thin nanoelement: Numerical simulation study

Berkov

Gorn

2005

Phys. Rev. B

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“…Here, the magnetization dynamics becomes complicated due to excitation of incoherent spin-waves when I > I C CONV . As indicated by an arrow, secondary peaks are observed at about half of the frequency of main peaks, corresponding to the precession of end domains [31]. In the non-local, self-consistent simulations, similar secondary peaks are observed, indicating deviations from a single domain state, but peak structures are much clearer than they are in the conventional simulations up to about 2.4 mA, which is larger than I C CONV (Fig.…”

Section: Spin Valvesmentioning

confidence: 72%

“…Whereas the conventional spin transfer torque and its interplay with the Oersted field tend to cause a large amplitude incoherent spin wave excitation [29][30][31][32], the positive lateral spin transfer torque effect captured by the self-consistent calculation tends to reduce spatial inhomogeneities (suppress spin waves) and leads to more coherent magnetization dynamics at low temperatures. This effect would be beneficial for microwave oscillators utilizing spin transfer torque, where a narrow linewidth is a key requirement.…”

Section: Discussionmentioning

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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“…Initial attempts of establishing tuneable STNOs used two homogeneously magnetized layers: one playing the role of a spin polarizer for the current and the other being the free, oscillating part, although these roles can hardly be separated in a very strict sense [14][15][16] . Single-domain nanopillars suffer from the disadvantage of exhibiting large linewidths (B100 MHz) due to inhomogeneous local field distributions 15 , as well as the necessity, in general, to apply external magnetic fields. STNOs exploiting the gyrotropic mode of vortices can overcome most of these difficulties, since they operate without applied field and display extremely narrow linewidths (in the order of MHz).…”

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confidence: 99%

Spin-torque-induced dynamics at fine-split frequencies in nano-oscillators with two stacked vortices

et al. 2015

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The gyrotropic rotation around the equilibrium position constitutes the fundamental excitation of magnetic vortices in nanostructures. The frequency of this mode varies with material and sample geometry, but is independent of the vortex handedness and its core direction. Here, we demonstrate that this degeneracy is lifted in a spin-torque oscillator containing two vortices stacked on top of each other. When driven by spin-polarized currents, such devices exhibit a set of dynamic modes with discretely split frequencies, each corresponding to a specific combination of vorticities and relative core polarities. The fine splitting occurs even in the absence of external fields, demonstrating that such devices can function as zero-field, multi-channel, nano-oscillators for communication technologies. It also facilitates the detection of the relative core polarization and allows for the eight non-degenerate configurations to be distinguished electrically, which may enable the design of multi-state memory devices based on double-vortex nanopillars.

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Excitations of incoherent spin-waves due to spin-transfer torque

Cited by 241 publications

References 17 publications

Magnetization precession due to a spin-polarized current in a thin nanoelement: Numerical simulation study

Magnetization precession due to a spin-polarized current in a thin nanoelement: Numerical simulation study

Self-consistent calculation of spin transport and magnetization dynamics

Spin-torque-induced dynamics at fine-split frequencies in nano-oscillators with two stacked vortices

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