Epitaxial films and ordered arrays of submicron structures of nickel and cobalt ferrites were deposited on Nb doped SrTiO₃ by pulsed laser deposition. X-Ray diffraction and atomic force microscopy showed that the films have a good crystalline quality and smooth surfaces. A larger number of phonon bands was observed in the polarization dependent Raman spectra of the ferrite films than expected for the cubic spinel structures. This is explained by short range ordering of the Ni²⁺ (or Co²⁺) and Fe³⁺ cations at the octahedral sites inducing a lowering of the symmetry. The same behavior was also observed in the Raman spectra measured for the submicron structures, suggesting the same cation distribution as in the films. The diagonal components of the dielectric function for nickel and cobalt ferrites are determined from ellipsometry in the 0.73–5 eV photon energy range. The absorption edge was analyzed using a bandgap model and the energies for the indirect and direct optical transitions were calculated. It was found that both nickel and cobalt ferrites are indirect bandgap materials with bandgaps of 1.65 eV and 1.42 eV, respectively, while the first direct transitions lie at 2.69 eV and 1.95 eV, respectively. Magneto-optical Kerr effect spectroscopy in combination with spectroscopic ellipsometry allowed the off-diagonal elements of the dielectric tensor to be determined in the energy range from 1.7 eV to 5 eV.

The characteristic mineral-free fibrous skeletons (made of structural protein-spongin) of H. communis (Demospongiae: Porifera) was used as a structural template in hydrothermal synthesis of hematite (α-Fe ₂ O ₃ ) nanoparticles.

Resonant Raman study reveals the noticeable effect of the ligand exchange on the nanocrystal (NC) surface onto the phonon spectra of colloidal CdTe NC of different size and composition. The oleic acid ligand exchange for pyridine ones was found to change noticeably the position and width of the longitudinal optical (LO) phonon mode, as well as its intensity ratio to overtones. The broad shoulder above the LO peak frequency was enhanced and sharpened after pyridine treatment, as well as with decreasing NC size. The low-frequency mode around 100 cm^-1which is commonly related with the disorder-activated acoustical phonons appears in smaller NCs but is not enhanced after pyridine treatment. Surprisingly, the feature at low-frequency shoulder of the LO peak, commonly assigned to the surface optical phonon mode, was not sensitive to ligand exchange and concomitant close packing of the NCs. An increased structural disorder on the NC surface, strain and modified electron-phonon coupling is discussed as the possible reason of the observed changes in the phonon spectrum of ligand-exchanged CdTe NCs.PACS: 63.20.-e, 78.30.-j, 78.67.-n, 78.67.Bf