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.
Highlights
Fundamental understanding of magnetization dynamics in ferromagnetic nanostructures is essential due to the potential applications in high-frequency information storage[1,2,3] and magnonic devices.[4,5,6,7,8,9,10] For these applications, a comprehensive knowledge of both the temporal and spatial profiles of ferromagnetic resonant modes is essential
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 is observed
We demonstrate direct probing of size-dependent magnetization dynamics in individual Ni80Fe20 (NiFe) circular disk of varying diameter {D = 2R : 1μm, 800nm, 500nm and 300nm} and fixed thickness L = 25 nm using micro-focused Brillouin Light Scattering (μ-BLS) spectroscopy
Summary
Fundamental understanding of magnetization dynamics in ferromagnetic nanostructures is essential due to the potential applications in high-frequency information storage[1,2,3] and magnonic devices.[4,5,6,7,8,9,10] For these applications, a comprehensive knowledge of both the temporal and spatial profiles of ferromagnetic resonant modes is essential. As the devices’ building blocks are miniaturized to achieve higher areal density, the size-dependent aspect of magnetization dynamics has become ever more important in designing future high performance devices. Diminishes due to an additional exchange energy contribution in smaller disks. These results may be useful in the design of high frequency information storage, logic and magnonic devices
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