Current-Driven Vortex Oscillations in Metallic Nanocontacts

Mistral, Q.; Kampen, M. van; Hrkac, G.; Kim, Joo-Von; Devolder, T.; Crozat, P.; Chappert, C.; Lagae, Liesbet; Schrefl, T.

doi:10.1103/physrevlett.100.257201

Cited by 219 publications

(227 citation statements)

References 18 publications

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“…This localization is due to the strong inhomogeneity of the CoFe stray field acting on the Py wire. In this sense, our system differs qualitatively from extended multilayer devices employing the point contact current injection 8 , where the localization of the ST-induced oscillations is caused by the strong non-linearity of the auto-oscillation modes (e.g., bullet 33 , vortex 34 or vortex-antivortex pairs 35,36,37 ). In our case, magnetization oscillations in the linear regime are already localized within the Py nanowire area under the CoFe nanomagnet due to the stray field form the CoFe nanomagnet.…”

Section: A General Features Of the Magnetization Oscillationsmentioning

confidence: 84%

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: A General Features Of the Magnetization Oscillationsmentioning

confidence: 84%

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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“…The particular cases of an in-plane current, [16][17][18] nanopillar magnetization dynamics under the influence of a perpendicular polarizer, [19][20][21][22][23][24][25][26][27][28] a vortexlike polarizer [29][30][31] or nanocontacts [32][33][34] were considered.…”

Section: Introductionmentioning

confidence: 99%

Limits for the vortex state spin torque oscillator in magnetic nanopillars: Micromagnetic simulations for a thin free layer

Aranda

González

Val

et al. 2010

Journal of Applied Physics

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Anomalous magnetic properties of 7nm single-crystal Co3O4 nanowires J. Appl. Phys. 111, 013910 (2012) High field-gradient dysprosium tips for magnetic resonance force microscopy Appl. Phys. Lett. 100, 013102 (2012) Dipolar interactions in magnetic nanowire aggregates J. Appl. Phys. 110, 123924 (2011) Dielectric and spin relaxation behaviour in DyFeO3 nanocrystals J. Appl. Phys. 110, 124301 (2011) Finite size versus surface effects on magnetic properties of antiferromagnetic particles Appl. Phys. Lett. 99, 232507 (2011) Additional information on J. Appl. Phys. We report micromagnetic simulations of magnetization dynamics of a vortex state in the free layer of a circular nanopillar excited by the spin transfer torque effect of a perpendicular to the layer ͑dot͒ plane spin-polarized electrical current. The magnetization of the reference layer ͑polarizer͒ is assumed to be fixed. A new regime of the dynamic magnetization response to the current is reported: vortex expelling from the dot, subsequent in-plane magnetization oscillations in single domain state, and the vortex return with an opposite core polarization. We analyze conditions ͑limits of the vortex state as a nano-oscillator͒ to achieve steady magnetization oscillations corresponding to a gyrotropic motion of the vortex core in terms of the current intensity. These conditions are formulated via the critical currents and vary greatly with the magnetic damping parameter and the cell size used for micromagnetic simulations. The existing experiments on the current induced magnetization dynamics in nanopillars and nanocontacts are discussed.

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“…Our direct observations of strongly coupled coaxial vortex motion demonstrates that while coupled vortices may exhibit a frequency response, their resultant motion are not equally coherent. This is critical for vortex spin-wave technologies whose essential features, such as linewidths, frequency agility and power 24 , are directly related to highly coherent gyrotropic motion and orbital amplitudes 12,25 . Compared with single vortex-and dipolar-coupled discs, exchange-coupled vortex discs possess a higher resonance, so adding another means of tuning the eigenfrequency through strong coupling interactions.…”

Section: Discussionmentioning

confidence: 99%

“…To the best of our knowledge, the direct observation of HF dynamic motion in coaxial strongly coupled vortex system has yet to be reported and will provide significant insights for applications such as spin-torque vortex oscillators (STVO). The performance metrics of STVOs, such as power output and spectral linewidths, are directly related to the vortex core rigidity, coherent gyrotropic motion, steady-state orbital amplitude and mode-coupled dynamics 1,2,12,19,24,25 . Here we present a direct imaging study of the driven dynamics in IC magnetic vortex disc heterostructures.…”

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confidence: 99%

Coherence and modality of driven interlayer-coupled magnetic vortices

et al. 2014

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The high-frequency dynamics of mode-coupled magnetic vortices have generated great interest for spintronic technologies, such as spin-torque nano-oscillators. While the spectroscopic characteristics of vortex oscillators have been reported, direct imaging of driven coupled magnetic quasi-particles is essential to the fundamental understanding of the dynamics involved. Here, we present the first direct imaging study of driven interlayer coaxial vortices in the dipolar-and indirect exchange-coupled regimes. Employing in situ highfrequency excitation with Lorentz microscopy, we directly observe the steady-state orbital amplitudes in real space with sub-5 nm spatial resolution. We discuss the unique frequency response of dipolar-and exchange-coupled vortex motion, wherein mode splitting and locking demonstrates large variations in coherent motion, as well as detail the resultant orbital amplitudes. This provides critical insights of the fundamental features of collective vortex-based microwave generators, such as their steady-state amplitudes, tunability and mode-coupled motion.

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Current-Driven Vortex Oscillations in Metallic Nanocontacts

Cited by 219 publications

References 18 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

Limits for the vortex state spin torque oscillator in magnetic nanopillars: Micromagnetic simulations for a thin free layer

Coherence and modality of driven interlayer-coupled magnetic vortices

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