We show that the optically induced spin wave spectra of nanoscale Ni80Fe20 (permalloy) antidot lattices can be tuned by changing the antidot shape. The spin wave spectra also show an anisotropy with the variation of the in-plane bias field orientation. Analyses show this is due to various quantized and extended modes, whose nature changes with the antidot shape and bias field orientation as a result of the variation of the internal magnetic field profile. The observed variation and anisotropy in the spin waves with the internal and external parameters are important for their applications in magnonic devices.

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Spin waves are investigated in Permalloy(Ni80Fe20)/Cobalt(Co) exchange spring bilayer thin films using Brillouin light scattering (BLS) experiment. The magnetic hysteresis loops measured by magneto-optical Kerr effect show a monotonic decrease in coercivity of the bilayer films with increasing Py thickness. BLS study shows two distinct modes, which are modelled as Damon-Eshbach and perpendicular standing wave modes. Linewidths of the frequency peaks are found to increase significantly with decreasing Py layer thickness. Interfacial roughness causes to fluctuate exchange coupling at the nanoscale regimes and the effect is stronger for thinner Py films. A quantitative analysis of the magnon linewidths shows the presence of strong local exchange coupling field which is much larger compared to macroscopic exchange field.

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Abstract-Highly ordered, self-organized TiO 2 nanotube arrays (TNA) have been successfully prepared by anodization of titanium foil in ethylene glycol electrolyte containing 0.01% ammonium fluoride (NH4F). The effect of variation of applied anodization voltage ranging from 50V to 57 V on the morphology of the TNA has been studied using field emission scanning electron microscope. The increase in applied voltage enhances average pore size from 34nm to 58nm and reduces wall thickness. Diffuse reflectance spectroscopy has been used to evaluate the amount of dye absorption on the surface of various TNA which reveals direct correlation between the dye absorption and the morphology of the sample.