Size-dependent magnetization dynamics in individual Ni80Fe20 disk using micro-focused Brillouin Light Scattering spectroscopy

Abstract

A direct and systematic investigation of the magnetization dynamics in individual circular Ni80Fe20 disk of diameter (D) in the range from 300 nm to 1 μm measured using micro-focused Brillouin Light Scattering (μ-BLS) spectroscopy is presented. At high field, when the disks are in a single domain state, the resonance frequency of the uniform center mode is observed to reduce with reducing disk’s diameter. For D = 300 nm, additional edge and end-domains resonant modes are observed due to size effects. At low field, when the disks are in a vortex state, a systematic increase of resonant frequency of magnetostatic modes in a vortex state with the square root of the disks’ aspect ratio (thickness divided by radius) is observed. Such dependence diminishes for disks with larger aspect ratio due to an increasing exchange energy contribution. Micromagnetic simulations are in excellent agreement with the experiments.

Tuning spin wave modes in yttrium iron garnet films with stray fields

“…The simulated results from Py dots as well as the YIG continuous film exhibited a single resonance mode. The resonance in the Py dots occurred at 8.20 GHz showing a central mode 30 in each dot which has been labeled as PyD-1 and the resonance for the continuous YIG film occurred at 4.78 GHz labeled as YIG-a. The simulations for the YIG antidot and YIG dot structures exhibited two resonance modes at 4.69 GHz and 4.10 GHz.…”