Optical path difference behind of spectacular game of light

AbstractThis work reports, in a general frame concerning the scientific explanations of wonderful effects from the daily life, on the physical basis behind the colorful images observed at the surface of various transparent films. Accordingly, a deeper view inside of the related interference phenomena is provided, along with a new didactical approach. The concept of interference of light is developed and the optical path difference is introduced as a crucial parameter in explaining the formation of the interference patterns. Particularization is done in case of thin film interference, explaining so the spectacular game of colors on the surface of transparent films, observed in nature

Mössbauer spectral study of the RFe11.5Ta0.5 (R=Tb, Dy, Ho, Er, and Lu) compounds

18 pages, 15 figures, 10 tables.-- PACS number(s): 75.50.Bb, 75.50.Ww, 76.80.+yThe paper presents an iron-57 Mössbauer spectral study of RFe11.5Ta0.5, with R=Tb, Dy, Ho, Er, Lu, and an evaluation of the different contributions to the hyperfine magnetic fields. The Mössbauer spectra have been analyzed with a model that considers both the distribution of the tantalum atoms in the near-neighbor environment of the iron atoms and the relative orientation of the hyperfine field and the principal axis of the electric field gradient. Their possible directions in the ThMn12 structure have been determined from a close examination of the point symmetry of each iron site. A local model for the hyperfine field which enables to determine their components from experimental data, has been developed and a calculation of the lattice dipolar hyperfine field in RFe11.5Ta0.5 has been performed. We have investigated in detail the origin and influence of the contributions to the hyperfine field coming from self 3d polarization, the iron and rare earth transferred fields and the orbital and dipolar hyperfine fields. The iron and rare earth transferred fields have been analyzed for RFe11.5Ta0.5 and other rare earth-iron intermetallic compounds. From this analysis it is shown that the iron transferred fields are different at each crystallographic site, and comparable to the self 3d polarization contributions, and that the rare earth transferred field is mainly originated by the indirect exchange between the rare earth 4f and iron 3d electrons.This work was financed by the MAT 02/166 and MAT 2000/0107/P4-02 MCYT projects (Spanish government). C.P. thanks MCYT for financial Grant No. PN73195091Y.Peer reviewe

Zr-Based Heusler Compounds for Biomedical Spintronic Applications

Current advances in microelectronics depend on novel approaches based on the synergistic use of charge and spin dynamics of electrons in multi-functional materials. Such new concepts have already found practical applications in magnetoelectronics or spintronics (e.g., spin valves or nonvolatile memory components). For efficient spintronic devices, it is desirable to have an enhanced spin polarization, that, to work with nearly 100% spin-polarized currents. Since half metallic materials have electrons of unique spin polarization around the Fermi level (finite density of states in only one spin channel), they are promising candidates for use as spin injectors in spintronic devices. Although the Heusler compounds reported in the literature presenting half-metallic ferro/ferrimagnetism are numerous, only a few contain elements with low toxicity, as for example zirconium, being also susceptible of convenient preparation and processing. Therefore, in future, zirconium-based compounds could become a much suitable alternative to the presently known cobalt, iron, chromium, titanium, manganese, or scandium-based half-metallic Heusler compounds, being of interest especially in biomedical spintronic related applications involved in corrosive/active environment

Spectroscopic investigations on PVDF-Fe2O3 nanocomposites

Polyvinylidene fluoride-iron oxide (PVDF-Fe2O3) nanocomposites have been obtained my melt mixing of PVDF with Fe2O3 nanoparticles. The interactions between the polymeric matrix and the nanofiller have been investigated by wide angle X-ray scattering (WAXS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, using both red and green excitations (lasers). WAXS, FTIR, and Raman spectra confirm that all samples contain α PVDF as the major crystalline form of the polymeric matrix. Experimental data revealed small changes in the positions of X-ray lines as well as modifications of the width of X-ray lines upon loading by Fe2O3 nanoparticles. FTIR and Raman spectra are dominated by the lines of the polymeric matrix. Within the experimental errors, the positions of Raman lines are not affected by the wavelength of the incoming electromagnetic radiation, although they are sensitive to the strain of the polymeric matrix induced by addition of the nanofiller. The loading of the polymeric matrix with nanoparticles stretches the macromolecular chains, affecting their vibrational spectra (FTIR and Raman). A complex dependence of the positions of some Raman and FTIR lines on the loading with Fe2O3 is reported. The manuscript provides a detailed analysis of the effects of nanofiller on the position of WAXS, FTIR, and Raman lines

BIO-FUELS EMPLOYABLE AT ALL SEASONS OBTAINED BY VEGETABLE OILS PROCESSING

Rezumat. Ca şi combustibilii pe bază de petrol, bio-combustibili