Local ferromagnetic resonance imaging with magnetic resonance force microscopy.

We report nanoscale scanned probe ferromagnetic resonance force microscopy (FMRFM) imaging of individual ferromagnetic microstructures. This reveals the mechanism for high spatial resolution in FMRFM imaging: the strongly inhomogeneous local magnetic field of the cantilever mounted micromagnetic probe magnet used in FMRFM enables selective, local excitation of ferromagnetic resonance (FMR). This approach, demonstrated here in individual permalloy disks, is straightforwardly extended to excitation of localized FMR modes, and hence imaging in extended films.

Missing 2k(F) response for composite fermions in phonon drag.

The response of composite fermions to large wave vector scattering has been studied through phonon drag measurements. While the response retains qualitative features of the electron system at zero magnetic field, notable discrepancies develop as the system is varied from a half-filled Landau level by changing density or field. These deviations, which appear to be inconsistent with the current picture of composite fermions, are absent if half filling is maintained while changing density.

Excitation spectra of surface-enhanced Raman scattering on silver-island films.

Both the spectral dependence and the magnitude of the excitation spectra of surface-enhanced Raman scattering are found to be quantitatively related to the absorption spectra for silver-island films. This relationship is maintained even when the local electromagnetic enhancement at the islands is varied by coating the film with a layer of absorbing dye molecules. The results illustrate a simple experimental way to determine independently the role of the electronic plasma resonances in the enhancement process on these films and shed new insights into the details of the electromagnetic interactions responsible for surface-enhanced Raman scattering.

Fluorescent lifetimes of molecules on silver-island films.

The fluorescence of molecules on silver-island films exhibits nonexponential decay and is several orders of magnitude more rapid than on a silica surface, while the total emission intensity is slightly increased. This behavior results from the electromagnetic coupling between the fluorescing molecules and the plasmon resonances of the silver islands. We obtain good agreement with a model that uses the same theory for the electromagnetic coupling as has been used to account for surface-enhanced Raman scattering.

Optical absorption resonances of dye-coated silver-island films.

We have used Mie theory to account for the features of the transmission spectra of dye-coated silver-island films. The unusual behavior of the spectra arises from the effect of the dispersion and damping of the optical response of the absorbing coating on the structural resonances of the silver islands. Our modeling indicates that the power dissipation in the dye coating is enhanced compared with the dissipation of dye deposited on a nonresonant structure.