Theory for a dissipative droplet soliton excited by a spin torque nanocontact

Hoefer, Mark; Silva, Thomas J.; Keller, Mark W.

doi:10.1103/physrevb.82.054432

Cited by 140 publications

(265 citation statements)

References 39 publications

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“…Depending on the geometry and magnetic properties of the free layer, propagating spin waves (SWs) [5][6][7] , solitonic modes [8][9][10][11] , vortex gyration 12,13 , and magnetic dissipative droplets [14][15][16][17] have been observed. STOs can also be used to generate SWs in physically extended thin films, which is of particular interest for future magnonic applications 18,19 .…”

Section: Introductionmentioning

confidence: 99%

Mode-coupling mechanisms in nanocontact spin-torque oscillators

et al. 2015

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Spin torque oscillators (STOs) are devices that allow for the excitation of a variety of magnetodynamical modes at the nanoscale. Depending on both external conditions and intrinsic magnetic properties, STOs can exhibit regimes of mode-hopping and even mode coexistence. Whereas modehopping has been extensively studied in STOs patterned as nanopillars, coexistence has been only recently observed for localized modes in nanocontact STOs (NC-STOs) where the current is confined to flow through a NC fabricated on an extended pseudo spin valve. By means of electrical characterization and a multi-mode STO theory, we investigate the physical origin of the mode coupling mechanisms favoring coexistence. Two coupling mechanisms are identified: (i) magnon mediated scattering and (ii) inter-mode interactions. These mechanisms can be physically disentangled by fabricating devices where the NCs have an elliptical cross-section. The generation power and linewidth from such devices are found to be in good qualitative agreement with the theoretical predictions, as well as provide evidence of the dominant mode coupling mechanisms.

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Section: Introductionmentioning

confidence: 99%

Mode-coupling mechanisms in nanocontact spin-torque oscillators

et al. 2015

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“…While originally developed to achieve zerofield operation, these STNOs were later shown to be able to nucleate and sustain so-called magnetic droplet solitons [40][41][42][43][44], which are the dissipative analog of the magnon drop solitons suggested in the 1970s [22,24]. While the magnetic droplet is of great fundamental interest in itself, it also promises significant advantages in both microwave and memory applications.…”

Section: Introductionmentioning

confidence: 99%

Magnetic droplet solitons in orthogonal spin valves

Chung

Mohseni

Eklund

et al. 2015

Low Temperature Physics

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We review the recent experimental advancements in the realization and understanding of magnetic droplet solitons generated by spin transfer torque in orthogonal nanocontact based spin torque nanooscillators (STNOs) fabricated on extended spin valves and spin valve nanowires. The magnetic droplets are detected and studied using the STNO microwave signal and its resistance, the latter both quasistatically and time-resolved. The droplet nucleation current is found to have a minimum at intermediate magnetic field strengths and the nature of the nucleation changes gradually from a single sharp step well above this field, mode-hopping around the minimum, and continuous at low fields. The mode-hopping and continuous transitions are ascribed to droplet drift instability and re-nucleation at different time scales, which is corroborated by time-resolved measurements. We argue that the use of tilted anisotropy fixed layers could reduce the nucleation current further, move the nucleation current minimum to lower fields, and potentially remove the need for an applied magnetic field altogether. Finally, evidence of an edge mode droplet in a nanowire is presented. PACS: 75.30.Ds Spin waves;75.75.-c Magnetic properties of nanostructures.

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“…Up to date, two major STNO geometries have been studied: (i) spin valve nanopillars in which propagation of magnetic excitations is restricted by the ferromagnet boundaries in all three spatial dimensions (zero-dimensional systems, 0D) 5,27,28 and (ii) point contacts to spin valves in which magnetic excitations can propagate in the plane of the spin valve (twodimensional systems, 2D) 6,8,11,12,29 . The two-dimensional systems offer the advantage of phase locking of nearby STNOs via interaction by spin waves propagating in the common ferromagnetic free layer 11,12 .…”

Section: Introductionmentioning

confidence: 99%

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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Theory for a dissipative droplet soliton excited by a spin torque nanocontact

Cited by 140 publications

References 39 publications

Mode-coupling mechanisms in nanocontact spin-torque oscillators

Mode-coupling mechanisms in nanocontact spin-torque oscillators

Magnetic droplet solitons in orthogonal spin valves

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

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