Images of a Spin-Torque-Driven Magnetic Nano-Oscillator

Yu, Xiaowei; Pribiag, Vlad; Acremann, Yves; Tulapurkar, Ashwin; Tyliszczak, Tolek; Chou, Kang Wei; Bräuer, Björn; Li, Z. P.; Lee, O. J.; Gowtham, Praveen; Ralph, Daniel; Buhrman, R. A.; Stöhr, J.

doi:10.1103/physrevlett.106.167202

Cited by 47 publications

(34 citation statements)

References 24 publications

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“…The development may lead to innovative measurements such as spin polarization in vortex structures measured under AC excitations, and may impact several diverse fields within nanomagnetism. For example, the accuracy of recent measurements of static vortex shape and core trajectories in spin torque nano-oscillators 24 can be re-examined with the improved resolution of electron microscopy. Also, with advances in sensitivity, the timeaveraged and high-resolution imaging technique can be extended to image spin wave patterns in magnonic crystals 25 , as well as realspace studies of nodal patterns in arrays of phase-locked spin torque nano-oscillators 26 acting as spin-wave point sources.…”

Section: Discussionmentioning

confidence: 99%

Direct dynamic imaging of non-adiabatic spin torque effects

et al. 2012

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spin-transfer torques offer great promise for the development of spin-based devices. The effects of spin-transfer torques are typically analysed in terms of adiabatic and non-adiabatic contributions. Currently, a comprehensive interpretation of the non-adiabatic term remains elusive, with suggestions that it may arise from universal effects related to dissipation processes in spin dynamics, while other studies indicate a strong influence from the symmetry of magnetization gradients. Here we show that enhanced magnetic imaging under dynamic excitation can be used to differentiate between non-adiabatic spin-torque and extraneous influences. We combine Lorentz microscopy with gigahertz excitations to map the orbit of a magnetic vortex core with < 5 nm resolution. Imaging of the gyrotropic motion reveals subtle changes in the ellipticity, amplitude and tilt of the orbit as the vortex is driven through resonance, providing a robust method to determine the non-adiabatic spin torque parameter β = 0.15 ± 0.02 with unprecedented precision, independent of external effects.

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Section: Discussionmentioning

confidence: 99%

Direct dynamic imaging of non-adiabatic spin torque effects

et al. 2012

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“…Spin torque forms the basis for tunable microwave nano-oscillators in confined nanopillar structures 3 and nanocontacts abutting an extended ferromagnet 4 . Most nanopillar dynamics can be reasonably described by single-domain modeling 5 with the notable exception of gyrotropic vortex motion 6 . In contrast, nanocontacts enable the excitation of radiating [7][8][9] and localized, coherently precessing, nonlinear wave states 8 .…”

Section: Introductionmentioning

confidence: 99%

Propagation and control of nanoscale magnetic-droplet solitons

2012

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The propagation and controlled manipulation of strongly nonlinear, two-dimensional solitonic states in a thin, anisotropic ferromagnet are theoretically demonstrated. It has been recently proposed that spin-polarized currents in a nanocontact device could be used to nucleate a stationary dissipative droplet soliton. Here, an external magnetic field is introduced to accelerate and control the propagation of the soliton in a lossy medium. Soliton perturbation theory corroborated by two-dimensional micromagnetic simulations predicts several intriguing physical effects, including the acceleration of a stationary soliton by a magnetic field gradient, the stabilization of a stationary droplet by a uniform control field in the absence of spin torque, and the ability to control the soliton's speed by use of a time-varying, spatially uniform external field. Soliton propagation distances approach 10 µm in low loss media, suggesting that droplet solitons could be viable information carriers in future spintronic applications, analogous to optical solitons in fiber optic communications.

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“…The magnetic vortex is a stable structure that can be the actual ground state of a ferromagnetic nanodisk owing to the confining nature of a disk; in addition, the vortex has topological charge, enhancing the stability of this structure. Recently gyrotropic oscillations driven by spin-torque have been observed [17][18][19] in nanopillar structures. In a large nonconfined ferromagnetic film the ground state is the uniform ferromagnetic state, but the Oersted field about a nanocontact current can induce vortex formation [20][21][22][23][24] with spin-torque driving gyrotropic motion.…”

Section: Introductionmentioning

confidence: 99%

Vortex-antivortex dynamics driven by spin-torque in a nanocontact

Zaspel

Kireev

2015

Low Temperature Physics

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A spin-polarized current in a nanocontact has been shown to induce the formation of a magnetic vortex at the nanocontact by the Oersted field, and spin-torque drives the vortex core in an elliptical orbit about the nanocontact. For the case of an external in-plane magnetic field in an extended free layer, the magnetization will be uniform far from the nanocontact, implying that vortex formation must be accompanied by the formation of an antivortex. Using the Thiele approach to describe the vortex-antivortex dynamics it is shown that the frequency of gyrotropic motion of the vortex is a function of the nanocontact current which is linear for large vortex-antivortex separations and it becomes nonlinear as the separation is decreased. The equilibrium vortexantivortex separation can be controlled by the nanocontact current as well as the external magnetic field. PACS: 75.10.Hk Classical spin models; 75.75.Jn Dynamics of magnetic nanoparticles; 73.90.+f Other topics in electronic structure and electrical properties of surfaces, interfaces, thin films, and low-dimensional structures.

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Images of a Spin-Torque-Driven Magnetic Nano-Oscillator

Cited by 47 publications

References 24 publications

Direct dynamic imaging of non-adiabatic spin torque effects

Direct dynamic imaging of non-adiabatic spin torque effects

Propagation and control of nanoscale magnetic-droplet solitons

Vortex-antivortex dynamics driven by spin-torque in a nanocontact

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