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Journal: Journal of Alloys and Compounds

Authors: S.Azadian, M.M.Tehranchi, S. MortezaMohseni, S. MajidMohseni

Abstract: Understand and control of the Gilbert damping, a fundamentally important magnetodynamic characteristic of magnetic materials is crucial for magnonics and high frequency applications. In this paper, we demonstrate the microwave irradiation as an easy and effective technique to control and reduce the damping factor of permalloy (Ni80Fe20) thin films deposited on SiO2 substrate. Based on different irradiation times, damping decreases by ∼16% in a short interval time of few minutes and increases within longer irradiation times. We found that within such short irradiation time, before significant changes occur in its structure, determined by XRD and probed by SEM, AFM, and conductivity measurements, the major influence on the damping factor is the “aspect” of the surface of the film. We found that there is a consistent experimental and theoretical behavior of surface roughness and correlation length that explains the trend of the damping factor. Finally, with irradiation for very long times, cracks at the surface appear due to the different absorption and heat coefficients of permalloy layer and SiO2 substrate, which leads to increment of the resistivity and oxidation of the permalloy and large enhancement of the damping factor. Our achievements are useful not only for control of the damping factor, but for evaluation of microwave irradiation threshold where material properties change which are highly valuable for magnonics devices.
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