Ferromagnetic Resonance Modes in the Exchange-Dominated Limit in Cylinders of Finite Length

Abstract

We analyze the magnetic mode structure of axially-magnetized, finite-length, nanoscopic cylinders in a regime where the exchange interaction dominates, along with simulations of the mode frequencies of the ferrimagnet yttrium iron garnet. For the bulk modes we find that the frequencies can be represented by an expression given by Herring and Kittel by using wavevector components obtained by fitting the mode patterns emerging from these simulations. In addition to the axial, radial, and azimuthal modes that are present in an infinite cylinder, we find localized "cap modes" that are "trapped" at the top and bottom cylinder faces by the inhomogeneous dipole field emerging from the ends. Semi-quantitative explanations are given for some of the modes in terms of a one-dimensional Schrodinger equation which is valid in the exchange dominant case. The assignment of the azimuthal mode number is carefully discussed and the frequency splitting of a few pairs of nearly degenerate modes is determined through the beat pattern emerging from them.

Exploring the Microstructural Effect of FeCo Alloy on Carbon Microsphere Deposition and Enhanced Electromagnetic Wave Absorption

“…For the microwave absorption band spanning 2-18 GHz, domain wall resonance and hysteresis loss can be disregarded [62]. According to Aharoni's theory [63], the resonance peaks observed in the 2-8 GHz range of the tanδμ curve were attributed to natural resonance, while those in the higher frequency range correspond to exchange resonance. Additionally, eddy current effects constituted a significant contributor to magnetic loss [64].…”