Magnetic droplet solitons generated by pure spin currents

Divinskiy, B.; Urazhdin, Sergei; Demidov, V. E.; Kozhanov, Alexander; Носов, А. П.; Ринкевич, А. Б.; Demokritov, S. O.

doi:10.1103/physrevb.96.224419

Cited by 30 publications

(23 citation statements)

References 41 publications

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“…At higher currents, the power rapidly increases, while the linewidth decreases, consistent with the theory of nonlinear oscillators [41,42]. Figure 4(h) shows that the integral microwave generation intensity decreases with increasing out-of-plane field H > 960 Oe, suggesting that the size of the precessing region and/or the amplitude of dynamics decrease with increasing field, consistent with the previous studies of the droplet mode [15,38,43]. The minimum full width at half maximum (FWHM) and the integral intensity P int of spectra obtained at the current I p corresponding to the highest peak PSD [Figs.…”

Section: B Spectral Characteristics Of Vnc-shno At 60 Ksupporting

confidence: 89%

“…4(j-k)] are the largest at small fields, with the largest F W HM of 11 MHz observed at H = 800 Oe. The linewidth broadening at small fields is likely associated with the phase noise due to the inhomogeneous distribution of the ef-fective field (including the local variations of magnetic anisotropy and current-induced Oersted fields) coupled with the droplet drift instabilities [38][39][40][43][44][45]. We now address the thermal effects on the spectral coherence of the generated microwave signals, and their relation to the dynamical mode structure of VNC-SHNO.…”

Section: B Spectral Characteristics Of Vnc-shno At 60 Kmentioning

confidence: 98%

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Magnetic Droplet Mode in a Vertical Nanocontact-Based Spin Hall Nano-Oscillator at Oblique Fields

Chen,

Urazhdin,

Zhou

et al. 2020

Phys. Rev. Applied

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We experimentally demonstrate a new type of spin Hall nano-oscillator based on a vertical nanocontact fabricated on a Pt/[Co/Ni] multilayer. We analyze the spectral characteristics of the nano-oscillator as a function of current, magnetic field, and temperature. At sufficiently large currents, the oscillator exhibits dynamics at a frequency far below the ferromagnetic resonance, which at large fields exhibits a redshift with increasing current. At smaller fields and low temperatures, the frequency becomes nearly current-independent, with a well-defined threshold current I th. These distinct spectral characteristics of the demonstrated nano-oscillator can be explained by the formation of the magnetic droplet-a dissipative magnetic soliton stabilized by the local injection of spin current produced by the spin Hall effect in Pt. The minimum linewidth exhibits a linear temperature dependence, suggesting single-mode dynamics, and enabling coherent magnetization auto-oscillation at room temperature. The demonstrated nano-oscillator geometry provides new opportunities for the development of active nanomagnetic devices, and optimization of their spectral characteristics for applications in microwave technology and spin-wave logic.

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Section: B Spectral Characteristics Of Vnc-shno At 60 Ksupporting

confidence: 89%

Section: B Spectral Characteristics Of Vnc-shno At 60 Kmentioning

confidence: 98%

Magnetic Droplet Mode in a Vertical Nanocontact-Based Spin Hall Nano-Oscillator at Oblique Fields

Chen,

Urazhdin,

Zhou

et al. 2020

Phys. Rev. Applied

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“…There has been clear evidence for droplet soliton formation in ferromagnetic materials with perpendicular magnetic anisotropy [8][9][10][11][12][13][14][15][16][17], including direct images taken using x-ray microscopy [4,18]. Electrical measurements of voltage across the nanocontact, both ac and dc, provide an understanding of droplet modes due to the giant magnetoresistance effect.…”

Section: Introductionmentioning

confidence: 99%

Multiple magnetic droplet soliton modes

et al. 2019

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Droplet solitons are large amplitude localized spin-wave excitations that can be created in magnetic thin films with uniaxial anisotropy by a spin-polarized current flowing through an electrical nanocontact. Here, we report a low-temperature (4 K) experimental study that shows there are multiple and, under certain conditions, combinations of droplet modes, each mode with a distinct high-frequency spin precession (tens of gigahertz). Low-frequency (1 GHz) voltage noise is used to assess the stability of droplet modes. It is found that droplets are stable only in a limited range of applied field and current, typically near the current and field at which they nucleate, in agreement with recent predictions. Applied fields in the film plane favor multiple droplet modes, whereas fields perpendicular to the film plane tend to stabilize a single droplet mode. Micromagnetic simulations are used to show that spatial variation in the energy landscape in the nanocontact region (e.g., spatial variation of magnetic anisotropy or magnetic field) can lead to quantized droplet modes and low-frequency mode modulation, characteristics observed in our experiments.

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“…1b). As a consequence, the current dependence of the auto-oscillation frequency again becomes negative 57,58 , the generated spin waves self-localize, and can eventually nucleate magnetic droplet solitons 49,50,[59][60][61][62] .…”

Section: Introductionmentioning

confidence: 99%

Spin-orbit torque–driven propagating spin waves

et al. 2019

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Spin-orbit torque (SOT) can drive sustained spin wave (SW) auto-oscillations in a class of emerging microwave devices known as spin Hall nano-oscillators (SHNOs), which have highly non-linear properties governing robust mutual synchronization at frequencies directly amenable to high-speed neuromorphic computing. However, all demonstrations have relied on localized SW modes interacting through dipolar coupling and/or direct exchange. As nanomagnonics requires propagating SWs for data transfer, and additional computational functionality can be achieved using SW interference, SOT driven propagating SWs would be highly advantageous. Here, we demonstrate how perpendicular magnetic anisotropy can raise the frequency of SOT driven auto-oscillations in magnetic nano-constrictions well above the SW gap, resulting in the efficient generation of field and current tunable propagating SWs. Our demonstration greatly extends the functionality and design freedom of SHNOs enabling long range SOT driven SW propagation for nanomagnonics, SW logic, and neuromorphic computing, directly compatible with CMOS technology.

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Magnetic droplet solitons generated by pure spin currents

Cited by 30 publications

References 41 publications

Magnetic Droplet Mode in a Vertical Nanocontact-Based Spin Hall Nano-Oscillator at Oblique Fields

Magnetic Droplet Mode in a Vertical Nanocontact-Based Spin Hall Nano-Oscillator at Oblique Fields

Multiple magnetic droplet soliton modes

Spin-orbit torque–driven propagating spin waves

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