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We demonstrate a magneto-optic technique to measure Brownian relaxation of magnetic nanoparticles suspended in liquids. We used AC susceptibility data as a function of frequency of the applied AC magnetic field to verify that the results agree with those obtained via a conventional inductive detection technique. However, compared with a commercial AC susceptometer using the conventional detection scheme, our magneto-optic setup is able to detect a density of nanoparticles at least three orders smaller. This technique has the potential of being used as a sensor for magnetic nanoparticles such as in local temperature, viscoelasticity, or molecular-binding measurements.

Aluminate glasses containing 45–71.5 mol% alumina, 10–40 mol% rare earth oxide, and 0–30 mol% silica were synthesized from precursor oxides. The glass transition and crystallization temperatures were determined by differential scanning calorimetry; the structural and mechanical properties were investigated by Raman and Brillouin spectroscopy. The range of the supercooled liquid region varies from ∼40 °C to 200 °C, providing a useful working range for compositions with 5–30 mol% silica. Raman scattering showed the presence of isolated SiO 4 species that strengthen the network-forming structure, enhance glass formation, and stabilize the glass even when they are present at fairly low concentrations. Sound velocities were measured by Brillouin scattering. From these and other values, various elastic moduli were calculated. The moduli increased with both aluminum and rare earth content, as did the hardness of the glasses. Young’s modulus was in the range 118–169 GPa, 60–130% larger than that for pure silica glass.

Brillouin scattering results from the interaction of photons with thermal excitations in a medium. The energy and propagation direction of the photons are modified by the interaction giving rise to a measurable frequency shift. Because the excitations are not related to the order existing in the medium, they can be observed in gases, fluids, or solids, ordered (crystals) as well as disordered (amorphous or glasses). In crystals, the measured frequency shift depends on the propagation direction of the excitations (phonons). Hence, Brillouin scattering is well adapted to study phase transitions, driven either by pressure, temperature, or a combination of them. The use of the technique is illustrated by two examples: berlinites under pressure, and a high temperature study of silicate melts.

A complete description of the first-order Raman and Brillouin spectra of single-crystal aluminum nitride is provided. The frequency has been measured and the symmetry identified of each of the Raman-active zone-center optic modes, and the five independent elastic constants have been measured. The widths of the principal Raman modes increase with increasing oxygen content up to a critical value of approximately 1 at. %, after which they are constant. This behavior supports the hypothesis of a change in the nature of the oxygen defect at that concentration.

A series of Cu/Pd superlattices with composition modulation wavelengths (Λ's) ranging from 1.6 to 3.5 nm and a strong [111] growth texture were prepared by electron beam evaporation. The elastic properties of the films were examined using the methods of uniaxial tension tests [a Young's modulus (1/s11), where sij is an elastic compliance] with the applied load parallel to the plane of the Cu/Pd interface and Brillouin scattering [a shear modulus (1/s44) with the shear waves parallel to the plane of the Cu/Pd interface]. Also, the films were characterized using both x-ray diffraction and high-resolution electron microscopy; this was done to assess the effect of the nanostructure on a possible “supermodulus effect.” The films are nanostructurally very similar to the superlattice films employed in previous studies at Northwestern in which a supermodulus effect was reported. But, contrary to previous studies, no anomalous behavior was observed for the measured elastic properties of the thin films. Therefore the present results negate the earlier results and cast a serious doubt on the existence of a supermodulus effect.

Brillouin scattering measurements have been carried out on single‐crystal lattice‐matched TiN/(V0.6Nb0.4)N and mismatched TiN/NbN superlattices. Measured surface wave velocities were found to be independent of superlattice wavelength over the entire range investigated, 1.5–30 nm, and were averages of the measured velocities of pure homogeneous TiN, NbN, and (V0.6Nb0.4)N. These results indicate that there is no anomaly in the C44 elastic constant. X‐ray diffraction results from the superlattices indicated that the average lattice spacing did not vary with wavelength. This is consistent with previous observations where elastic anomalies were related to changes in lattice spacing. The absence of a correlation between the C44 elastic constant and previously reported hardness enhancements indicates that the latter are not caused by anomalies in C44; they could, however, be correlated with other elastic moduli.

The modulation wavelength dependence of the surface‐wave velocity in Cu/Ni superlattices has been investigated using Brillouin scattering. It is the first compositionally modulated system to be studied by this technique and the first for which elastic properties have been determined by both ‘‘macroscopic’’ methods and Brillouin scattering. Contrary to the enhancements previously reported in the biaxial modulus and in the Young’s modulus, the modulus associated with the surface‐wave velocity shows no evidence of anomalous behavior.

We have used Brillouin scattering to measure the temperature dependence of the sound velocities of the longitudinal and transverse vibrational modes in various directions in small single crystals of monoclinic ZrO2. Using these velocities and the Christoffel equation, we have calculated the 13 elastic stiffness moduli between room temperature and the monoclinic—tetragonal transformation temperature.

The dynamics of individual magnetic vortices and vortex pairs confined in lithographically defined ferromagnetic ellipses were measured using a microwave reflection technique. Resonance frequencies were detected in the subgigahertz range for Ni80Fe20 (Permalloy) ellipses ranging in size from 3 by 1.5μm to 1 by 0.5μm, 40nm in thickness. Micromagnetic simulations indicate that the single mode observed for one vortex is a translational mode and that the two eigenmodes associated with a vortex pair correspond to coupled translational modes of vortices with parallel or antiparallel core polarizations. The single-vortex resonance scales inversely with the ellipse size, in agreement with the simulations and analytical theory.

The biaxial moduli of free‐standing metallic films have been determined from their behavior as elastically tensioned membranes. Errors due to thickness determination and warping of the films are eliminated, thereby opening up the possibility of solving a number of controversial issues. The method combines the determination of stress from the frequency of the membrane modes with optical measurements of strain. Tests on Ta and Ni films yield values of the biaxial modulus in good agreement with calculated literature data.