vortex resonance in flake-shaped ferromagnetic particles

What is it about?

Magnetic coatings are currently used to prevent electromagnetic interferences. Among such coatings, flake-shaped ferromagnetic particle composites are of great interest. So far, the investigations were focused on the natural spin resonance as the absorption mode (usually above 1 GHz). It is shown that a second absorption line of high-amplitude exists in all the investigated composites located between 50 MHz up to 300 MHz due to a vortex resonance inside the flux-closed magnetic particles.

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Why is it important?

This paper presents the first detailed investigation of the low-frequency absorption mode existing in flake-shaped ferromagnetic particle composites. Experimental dependences of the resonance frequency of this mode versus the nature of particles, their aspect ratio and the amplitude and orientation of both a polarizing and a pumping magnetic fields allow to identify such a resonance line as a vortex resonance mode within the flux-closed magnetic particles.