Microwave spectroscopy : Dynamical micromagnetism

We provide in this paper a detailed interpretation of the measured and simulated spin-wave spectra for Permalloy square dots in a Landau remanent configuration. Various semianalytical approaches are combined to show how the domain walls present in the Landau configuration may (i) confine low-frequency spin waves and (ii) set a triangular geometry for the propagation of higher frequency spin waves, which leads to a somehow counterintuitive quantization process. The knowledge gained from this study is finally used to reconstruct the magnetization process of the dots from the evolution of their microwave spectrum under an applied field.

Figure 1 : Absorption spectra measured and simulated in permalloy dots with 3 µm size and 30 nm thickness at remanence. Local susceptibility cartographies for each absorption peak.

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