Magnetic-field tunability of the vortex translational mode in micron-sized permalloy ellipses : Experiment and micromagnetic modeling

• A magnetic vortex confined in a magnetically soft ferromagnet with micron-sized dimensions possesses a characteristic dynamic excitation known as a translational mode that corresponds to spiral-like precession of the vortex core around its equilibrium position. We report micromagnetic modeling and experimental detection using a microwave reflection technique of the magnetic field tunability of this mode in 40 nm thick, 3x1.5 mu m(2) and 2x1 mu m(2) permalloy ellipses. At remanence the translational modes are detected at 77 and 118 MHz. The frequency shows a strongly anisotropic dependence on magnetic field applied in the plane of the ellipse. The frequencies more than double when a static field is applied along the hard (short) axis, whereas they are almost field-independent when the field is aligned with the easy (long) axis. Micromagnetic calculations reveal that the observed behavior is governed by the shape of the energy potential well that is influenced mainly by magnetostatic and Zeeman energies.

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NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

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Physics

Fysik

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