Stoichiometry dependence of the electrooptic response of Lithium Niobate

We investigated the electrooptic response of a set of Lithium Niobate crystals with Li concentration ranging from off-congruent to stoichiometric. Two accurate techniques based on interferometry and ellipsometry were employed to measure the electrooptic coefficients. No evidence was found of a possible enhancement of the EO response in stoichiometric Lithium Niobate with respect to the congruent one. The EO response showed a weak dispersion in the wavelength range 532-1550 nm

Misura dei coefficienti elettroottici di cristalli di Niobato di Litio stechiometrici e congruenti

The electrooptic coefficients r33, r13 and rc of congruent and stoichiometric Lithium Niobate crystals are measured at several wavelengths through interferometric and polarimetric techniques. Results are discussed and compared to the literature data

Misura dei coefficienti elettroottici di cristalli di Niobato di Litio stechiometrici e congruenti

The electrooptic coefficients r33, r13 and rc of congruent and stoichiometric Lithium Niobate crystals are measured at several wavelengths through interferometric and polarimetric techniques. Results are discussed and compared to the literature data

Magnetic and relaxometric properties of Mn ferrites

We present the magnetic properties and the 1H nuclear magnetic resonance dispersion profiles of Mn-ferrites-based compounds, as possible novel contrast agents (CAs) for magnetic resonance imaging (MRI). The samples consist of nanoparticles (NPs) with the magnetic core made of Mn1+xFe2−xO4. We have performed structural and morphological investigation by x-ray powder diffraction and transmission electron microscopy techniques and SQUID magnetometry experiments to investigate the magnetic behaviour of the samples. As required for MRI applications using negative CAs, the samples are superparamagnetic at room temperature, having blocking temperatures in the range 14–80 K. The longitudinal r1 and transverse r2 nuclear relaxivities appear to vary strongly with the magnetic core size, their values being comparable to commercial compounds in the high-frequency range. The experimental results suggest that our samples are suitable for high-frequency MRI imagers in general and in particular for the 3 T clinical imager

Magnetic Resonance Imaging Contrast Agents Based on Iron Oxide Superparamagnetic Ferrofluids

Novel systems based on suspensions of colloidal magnetic nanoparticles have been investigated as perspective superparamagnetic contrast agents (CA) for magnetic resonance imaging (MRI). The nanostructures that we have studied contain surfactant-capped magnetite (Fe3O4) inorganic cores with different controlled sizes, ranging from 5.5 to 12 nm. The as-synthesized nanostructures are passivated by hydrophobic surfactants and thus are fully dispersible in nonpolar media. The magnetic nanocrystals have been transferred into aqueous media by a procedure based on the surface intercalation and coating with an amphiphilic polymer shell. The MRI efficiency in contrasting images, i.e., the NMR relaxivities r1 and r2, have been compared with Endorem and Sinerem, commercial superparamagneticMRI contrast agents. We found that our nanostructures exhibit r1 and r2 relaxivities comparable to those of commercial CA over the whole frequency range. The MRI efficiency of our samples was related to their microstructural and magnetic properties. The transverse relaxivity r2, leading the contrast in “negative” superparamagnetic agents, was found to improve as the diameter of the inorganic core is increased. The NMR relaxometry profile confirmed the nature of the physical mechanisms inducing the increase of the nuclear relaxation rates at low (magnetic anisotropy) and high (Curie relaxation) fields