Self-Modulated Soliton Modes Excited in a Nanocontact Spin-Torque Oscillator

Puliafito, Vito; Siracusano, Giulio; Azzerboni, B.; Finocchio, G.

doi:10.1109/lmag.2014.2315973

Cited by 31 publications

(18 citation statements)

References 19 publications

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“…We note that the measured high-frequency dynamics, associated with the spin precession, has a blueshift with the applied current, different to predictions 10 and micromagnetic results 25 . We cannot explain it with our model and we attribute such effect to the appearance of an effective field perpendicular to the film plane due to the applied current (likely an Oersted-field effect from the leads).…”

contrasting

confidence: 86%

“…Some experiments have shown the presence of side bands in the precession frequency of the soliton 15 suggesting that the soliton might be undergoing drift instabilities. Micromagnetic studies have also predicted the side bands and attributed them to drift instabilities 15,25 . Our direct observation of the low frequency dynamics proves the existence of drift instabilities and explains why dc measurements fail to measure full magnetization reversal-showing on average just a fraction of the magnetization reversed.…”

mentioning

confidence: 99%

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Observation of droplet soliton drift resonances in a spin-transfer-torque nanocontact to a ferromagnetic thin film

Lendínez¹,

Statuto²,

Backes³

et al. 2015

Phys. Rev. B

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contrasting

confidence: 86%

mentioning

confidence: 99%

Observation of droplet soliton drift resonances in a spin-transfer-torque nanocontact to a ferromagnetic thin film

Lendínez¹,

Statuto²,

Backes³

et al. 2015

Phys. Rev. B

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“…The signal frequency after the jump is close to the Zeeman frequency, the prediction for a reversed droplet soliton, f Zeeman = γμ 0 H/(2π), where γ is the gyromagnetic ratio 1,2 . We note here that a single spectral line is observed, with no self-modulation 15 , as predicted for a sufficiently large free magnetic layer saturation magnetization or exchange constant 18 . Figure 1c shows that at 0.8 T (m z,P ≈ 0.73) we only observe the lower-frequency (magnetic droplet) excitation and the frequency increases (blueshifts) with increasing current (Fig.…”

supporting

confidence: 76%

Stable magnetic droplet solitons in spin-transfer nanocontacts

2014

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Magnetic thin films with perpendicular magnetic anisotropy have localized excitations that correspond to reversed, dynamically precessing magnetic moments, which are known as magnetic droplet solitons. Fundamentally, these excitations are associated with an attractive interaction between elementary spin-excitations and have been predicted to occur in perpendicularly magnetized materials in the absence of damping. Although damping suppresses these excitations, it can be compensated by spin-transfer torques when an electrical current flows in nanocontacts to ferromagnetic thin films. Theory predicts the appearance of magnetic droplet solitons in nanocontacts at a threshold current and, recently, experimental signatures of droplet nucleation have been reported. However, to date, these solitons have been observed to be nearly reversible excitations, with only partially reversed magnetization. Here, we show that magnetic droplet solitons exhibit a strong hysteretic response in field and current, proving the existence of bistable states: droplet and non-droplet states. In the droplet soliton state we find that the magnetization in the contact is almost fully reversed. These observations, in addition to their fundamental interest, are important to understanding and controlling droplet motion, nucleation and annihilation.

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“…1(c), where the core is partially reversed and the spins both in the core and in the droplet perimeter precess inphase. Although droplet theory [40] was developed for fully perpendicular spin valves, reported experiments [41,44] have used STNOs where the remanent state of the fixed layer is in the film plane, which can promote droplet instability and auto-modulation [41,[47][48][49]. In this orthogonal geometry, the current-field phase diagram of the droplet qualitatively differs from the theoretical predictions.…”

Section: Magnetic Droplet Nucleation Current Vs Fieldmentioning

confidence: 98%

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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Self-Modulated Soliton Modes Excited in a Nanocontact Spin-Torque Oscillator

Cited by 31 publications

References 19 publications

Observation of droplet soliton drift resonances in a spin-transfer-torque nanocontact to a ferromagnetic thin film

Observation of droplet soliton drift resonances in a spin-transfer-torque nanocontact to a ferromagnetic thin film

Stable magnetic droplet solitons in spin-transfer nanocontacts

Magnetic droplet solitons in orthogonal spin valves

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