Patricia B. Oliete

Magnetic behaviour of a hybrid polymer obtained from ethyl acrylate and the magnetic cluster Mn12O12(acrylate)16

The magnetic properties of polymers prepared by polymerization of the magnetic cluster Mn12O12(acrylate)16 with various portions of ethyl acrylate as co-monomer are reported. According to SAXS studies, the clusters are homogeneously distributed in the polymer. Ac susceptibility measurements show superparamagnet-like behaviour of the cluster-crosslinked polymers with relaxation following an Arrhenius law with τ0 = 4–8 × 10−8 s and an energy barrier in the range 45–65 K.

The enhanced Raman scattering of phonons in CaF2 and MgO samples containing Ca and Li colloids

We present Raman scattering spectra of CaF2 samples containing Ca colloids and of MgO:Li with Li precipitates. The samples have been prepared by different thermal and irradiation treatments in order to achieve a range of colloid radii and density. The sizes of the colloids are determined by their optical absorption bands. Exciting in the surface-plasmon band of the metal colloid we observe surface-enhanced Raman scattering (SERS) of the whole density of states of CaF2 or MgO phonons. The spectra are polarized and show a partial T2g character for CaF2. The intensity is enhanced as the laser energy approaches the colloid band maximum, where surface plasmons are excited. Comparing the results of different samples we find that the spectrum intensity is roughly proportional to the total amount of colloid material in the sample. In order to explain the appearance of the one-phonon density of states and its resonant behaviour we discuss the validity of the classical electromagnetic model and propose a mechanism consisting of surface-plasmon excitation followed by electron transfer from the metal to the host and de-excitation in the metal-host interface. In the host, electron-phonon interaction takes place, as in usual Stokes or antiStokes processes, giving rise to single-phonon modes. The lattice distortion and loss of periodicity in the vicinity of the colloid break the k=0 selection rule and account for the appearance of the whole density of states.

An electron paramagnetic resonance study of the tetragonally distorted ion in and

Chromium-doped [Formula: see text] and [Formula: see text] have been studied by both EPR and ENDOR spectroscopy. [Formula: see text] ions enter the fluorite structure in distorted substitution cation sites. In both matrices the distortion observed is tetragonal. X- and Q-band EPR measurements at temperatures between 4 and 300 K allowed us to determine the ion symmetry and the following spin-Hamiltonian parameters: [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] for [Formula: see text]; and [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] for [Formula: see text]. For [Formula: see text], the weak superhyperfine interaction of [Formula: see text] with the surrounding [Formula: see text] ions has been studied by both EPR and ENDOR techniques for [Formula: see text]. No ENDOR signals were detected for [Formula: see text]. The results are tentatively explained in terms of a Jahn - Teller effect corresponding to [Formula: see text] coupling strongly stabilized by lattice stresses, although other possible origins for the distortion cannot be completely ruled out.Chromium-doped and have been studied by both EPR and ENDOR spectroscopy. ions enter the fluorite structure in distorted substitution cation sites. In both matrices the distortion observed is tetragonal. X- and Q-band EPR measurements at temperatures between 4 and 300 K allowed us to determine the ion symmetry and the following spin-Hamiltonian parameters: , , , and for ; and , , , , and for . For , the weak superhyperfine interaction of with the surrounding ions has been studied by both EPR and ENDOR techniques for . No ENDOR signals were detected for . The results are tentatively explained in terms of a Jahn - Teller effect corresponding to coupling strongly stabilized by lattice stresses, although other possible origins for the distortion cannot be completely ruled out.

Directionally solidified fabrication in planar geometry of Al2O3-Er3Al5O12 eutectic composite for thermophotovoltaic devices

In this work Al2O3-Er3Al5O12 eutectic composite was manufactured in planar geometry departing from eutectic particles both produced by directional solidification using a CO2 laser system at rates of 180 and 720 mm/h. Microstructure and mechanical properties were investigated as a function of the growth rate. Homogeneous and interpenetrated microstructure was found with phase size strongly dependent on the growth rate, decreasing when the processing rate was increased. Thermal emission of eutectic composites was studied in function of thermal excitation by using CO2 laser radiation as a heating source. An intense narrow emission band at 1.55 µm matching with the sensitive region of the InGaAs photoconverter and a low emission band at 1 µm were obtained. Features of thermal emission bands were correlated with collecting angle, microstructure and laser power, and compared to those obtained from departing eutectic particles.

EPR of jahn-teller Cf2+ in CaF2, BaF2 and SrC12

We study chromium-doped CaF 2 , BaF 2 and SrCl 2 using EPR. Cr 2+ ions enter the fluorite structure in a substitutional Jahn-Teller distorted site. In CaF 2 the orthorhombic distortion is produced by two fluorine ions placed in the plane perpendicular to the defect axis. In BaF 2 and SrCl 2 the distortion is tetragonal. Measurements in the three different planes using both X and Q-band and at temperatures between 4 and 300 K allow us to determine most of the spin Hamiltonian parameters including those of hyperfine and superhyperfine interactions.

Enhanced raman scattering of phonons in CaF2 and MgO containing Ca and Li colloids

Abstract We present Raman scattering spectra of CaF2 samples with Ca colloids and MgO:Li with Li precipitates. The samples have been prepared by different thermal and irradiation treatment in order to achieve different colloid sizes. Exciting in the colloid surface-plasmon band we observe SERS of the whole density of states of CaF2 or MgO phonons, the intensity being enhanced when the excitation approaches the colloid band maximum. In order to explain the appearance of the one phonon density of states and the resonant behaviour we propose a mechanism consisting of surface plasmon and charge transfer excitation, superposed to the electromagnetic process.

Microestructura y propiedades mecánicas de fibras cerámicas eutécticas Al2O3/Er3Al5O12/ZrO2 procesadas por fusión zonal por laser

Resumen del trabajo presentado a la IV Reunion de Jovenes Investigadores en Coloides e Interfases, celebrada en Cordoba del 7 al 9 de febrero de 2018.Trabajo financiado por los proyectos SEROS (CGL 2014-55900-PL), DR3AM (CGL2015- CGL2014-55118) y Grupos Geotransfer y Analisis de Cuencas de la Universidad de Zaragoza. Es una contribucion del Institut de Recerca Geomodels y del Grup de Geodinamica i Analisi de Conques (2014SGR467).Resumen del trabajo presentado a la I Jornada de jovenes investigadores de ceramica y vidrio en el ICMA, celebrada el 20 de marzo de 2018 en la Universidad de Zaragoza.Gracias a todas las instituciones y organismos que han hecho posible este trabajo: al Ministerio de Economia y Competitividad por la beca FPI enmarcada en el proyecto MAT2011-22719, a la Universidad de Zaragoza y al Instituto de Ciencia de Materiales de Aragon.577 Pags.- Figs.- Tabls.- Fots. El contenido de los apartados que componen este libro es de exclusiva responsabilidad de los autores. Creative Commons License Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)Angel Larrea and Sonia Serrano-Zabaleta acknowledge funding from project MAT2012-30763 and the use of Servicio General de Apoyo a la Investigacion-SAI, Universidad de Zaragoza.Trabajo presentado al 8th International UHMWPE Meeting, celebrado en Torino (Italia) del 19 al 20 de octubre de 2017.Trabajo presentado al XI Congreso Nacional de Materiales celebrado en Zaragoza del 23 al 25 de junio de 2010.

An unprecedented mode of association in diselenadiazolyl radicals: crystal structures and magnetic properties of [p-XC6F4CNSeSeN]2 (X=Cl, Br)

The two title compounds are isostructural with pairs of diselenadiazolyl radicals associating in an unprecedented manner via an orthogonal interaction between singly occupied molecular orbitals which renders them essentially diamagnetic in the solid state.