Two-dimensional mapping of spin modes were calculated within the framework of the Dynamical Matrix Method for an elliptical nanoring with outer (inner) diameter of 1060 nm x 660 nm (550 nm x 230nm) and thickness of 20 nm. Results are thoroughly compared with the experimental spectra obtained though the micro-focused Brillouin Light Scattering (micro-BLS) technique, which allows to measure the intensity at a selected frequency as a function of the position over the single ring, and hence to produce similar dynamical maps. The corresponding experimental apparatus was recently set up at Perugia University and the samples were fabricated on a commercial oxidized silicon substrate by a combination of e-beam lithography, e-beam evaporation and lift-off processes. A thorough investigation of the mode dynamics on both in the vortex and saturated (“onion”) states was performed, allowing us to determine the mode symmetry and localization of spin resonances in both magnetic configurations. The theory about localization and splitting of spin excitation was applied to interpret experimental data. Moreover, we found experimental evidence of the existence of localized azimuthal modes at H=0 in the vortex state. We present also an effective dynamical method for determining the vortex chirality based on the detection of micro-BLS spectra on different ring arms. Finally, we draw considerations on the vortex-to-onion transition, with special attention to the soft mode involved: micro-BLS measurements show that its profile is actually antisymmetric with respect to the scattering plane, as predicted by calculations. This mode, as well as other antisymmetric modes, are undetectable through conventional measurements, but can give appreciable cross section by means of micro-BLS technique.
Two-dimensional mapping of spin modes in elliptical nanorings: a combined dynamical matrix and micro-focused Brillouin light scattering investigation
MONTONCELLO, Federico;
2009
Abstract
Two-dimensional mapping of spin modes were calculated within the framework of the Dynamical Matrix Method for an elliptical nanoring with outer (inner) diameter of 1060 nm x 660 nm (550 nm x 230nm) and thickness of 20 nm. Results are thoroughly compared with the experimental spectra obtained though the micro-focused Brillouin Light Scattering (micro-BLS) technique, which allows to measure the intensity at a selected frequency as a function of the position over the single ring, and hence to produce similar dynamical maps. The corresponding experimental apparatus was recently set up at Perugia University and the samples were fabricated on a commercial oxidized silicon substrate by a combination of e-beam lithography, e-beam evaporation and lift-off processes. A thorough investigation of the mode dynamics on both in the vortex and saturated (“onion”) states was performed, allowing us to determine the mode symmetry and localization of spin resonances in both magnetic configurations. The theory about localization and splitting of spin excitation was applied to interpret experimental data. Moreover, we found experimental evidence of the existence of localized azimuthal modes at H=0 in the vortex state. We present also an effective dynamical method for determining the vortex chirality based on the detection of micro-BLS spectra on different ring arms. Finally, we draw considerations on the vortex-to-onion transition, with special attention to the soft mode involved: micro-BLS measurements show that its profile is actually antisymmetric with respect to the scattering plane, as predicted by calculations. This mode, as well as other antisymmetric modes, are undetectable through conventional measurements, but can give appreciable cross section by means of micro-BLS technique.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.