Sunday, August 4, 2013

1308.0240 (Konstantin L. Metlov)

Vortex precession frequency and its amplitude-dependent shift in
cylindrical nanomagnets

Konstantin L. Metlov
Frequency of free magnetic vortex precession in circular soft ferromagnetic nano-cylinders (magnetic dots) of various sizes is an important parameter, used in design of spintronic devices (such as spin-torque microwave nano-oscillators) and characterization of magnetic nanostructures. Here, using recently developed collective-variable approach to non-linear dynamics of magnetic textures in planar nano-magnets, this frequency and its amplitude-dependent shift are computed analytically and plotted for the full range of cylinder geometries. The frequency shift is positive in large planar dots, but becomes negative in smaller and more elongated ones. At certain dot dimensions a zero frequency shift is realized, which can be important for enhancing frequency stability of magnetic nano-oscillators. Also, a simple analytical formula for vortex precession frequency in large (compared to the vortex core size) cylindrical magnetic dots is proposed, which covers a wide range of dot geometries (both planar and elongated).
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