Magnetically tunable composites exhibiting a pseudo plasmonic resonance

Resumen del trabajo presentado al 10th International ETOPIM (Electrical, Transport, and Optical Properties of Inhomogeneous Media), celebrado en jerusalem (Israel) del 21 al 26 de junio de 2015.Peer Reviewe

On the transparency of nanostructured alumina: Rayleigh-Gans model for anisotropic spheres

14 páginas, 6 figuras, 2 tablas.A light scattering model under the Rayleigh-Gans-Debye approximation has been developed for polycristalline alumina. The model states that transmittance of dense alumina ceramics basically depends not only on the maximum grain size but also on the preferential orientation of their c-axis, or texture. The effect of texture in transparency has been experimentally measured on several dense alumina samples with different grain size and compared to that obtained from x-ray Rietveld refinements with a very good agreement. The Rayleigh-Gans-Debye approximation also allows to represent optical data in a very simple way (logarithm of transmittance vs. the inverse of the wavelength square). Using these variables, a straight line is obtained for the Rayleigh-Gans-Debye approximation, its slope being proportional to the maximum grain size and textural parameter. Deviation from this law implies the presence of pores or grain of extremely large size.Peer reviewe

Fano-like resonance from disorder correlation in vacancy-doped photonic crystals

By preparing colloidal crystals with random missing scatterers, crystals are created where disorder is embodied as vacancies in an otherwise perfect lattice. In this special system, there is a critical defect concentration where light propagation undergoes a transition from an all but perfect reflector (for the spectral range defined by the Bragg condition), to a metamaterial exhibiting an enhanced transmission phenomenon. It is shown that this behavior can be phenomenologically described in terms of Fano-like resonances. The results show that the Fano's parameter q experiences a sign change signaling the transition from a perfect crystal exhibiting a reflectance Bragg peak, through a state where background scattering is maximum and Bragg reflectance reaches a minimum to a point where the system reenters a low scattering state recovering ordinary Bragg diffraction. A simple dipolar model considering the correlation between scatterers and vacancies is proposed and the reported evolution of the Fano-like scattering is explained in terms of the emerging covariance between the optical paths and polarizabilities and the effect of field enhancement in photonic crystal (PhC) defectsPID2021-124814NB-C21, PGC2018-095777-B-C22, PID2019-109905GA-C22, CEX2018-000805-M, UAM-CAM project (SI1/PJI/2019-00052

Determination of texture by infrared spectroscopy in titanium oxide–anatase thin films

12 pages, 6 figures, 4 tables, 2 appendix.-- PACS: 68.55.Jk; 78.66.Nk; 78.30.HvA theoretical model to determine the effective dielectric tensor of heterogeneous materials composed by anisotropic microcrystallites has been introduced to explain the infrared spectral features of textured thin films of uniaxial materials as the function of a textural parameter. This theoretical treatment is able to satisfactorily reproduce the experimental absorbance spectra of TiO2–anatase thin films chosen as a model system. Comparison of texture data obtained from infrared spectroscopy and x-ray diffraction are in good agreement which support the validity of the proposed model.Peer reviewe

Portland cement clinkers turned into garnets by spark plasma sintering

The feasibility of sintering Portland cement clinker powders by Spark Plasma Sintering (SPS) has been studied. Different SPSed compacts have been successfully obtained by this technique. The compacts have been characterized by means of X-Ray Diffraction, InfraRed spectroscopy, Scanning Electron Microscopy, Raman Microscopy and Vickers hardness. It is worth noting the finding that slight mineralogical variations in the starting compositions may induce dramatic changes, both in the final mineralogical composition and in the morphology, which can affect the properties of the SPSed compacts. Thus, we find that SPS allows artificial garnets to be obtained in the laboratory by applying pressures as low as 50 MPa, while they are materials that would require much higher pressures in natural environments (2-10 GPa). According to the Selsing model, it has been calculated that the material itself acts as a pressure amplifier at the micrometric level by a factor of 40-200 times. A new model describing the formation of garnets considering the emergence of two transitory eutectic liquids has been explained to justify this phenomenon. This result opens the door to looking for compositions for specific applications with high added value in the field (i.e. high hardness), mainly in the manufacturing of high-pressure (GPa) phases by applying relatively low pressures (MPa).The Authors acknowledge the financial support of the PID2020-119130 GB-I00 project funded by MCIN/AEI/10.13039/501100011033 and by CSIC under grant 201960E103. Thanks to the Official Laboratory for Testing of Construction Materials (LOEMCO, Getafe, Madrid, Spain) for free supply of the clinker sample

Procedimiento de obtención de materiales homogéneos compuestos ferroeléctrico-metal

Referencia OEPM: P200001701.-- Fecha de solicitud: 07/07/2000.-- Titular: Consejo Superior de Investigaciones Científicas (CSIC).Procedimiento de obtención de materiales homogéneos compuestos ferroeléctrico-metal que consiste en: mezcla de polvos de un material ferroeléctrico y un metal refractario, conformado de la mezcla homogénea obtenida, calcinación de las mezclas ya conformadas siguiendo un ciclo de calentamiento en dos etapas. Con este procedimiento se obtiene un material denso (mayor del 90% de densidad teórica), constituido por una matriz cerámica de naturaleza ferroeléctrica y partículas de un metal refractario homogéneamente dispersas en la matriz. Posee una constante dieléctrica de hasta cien veces superior a la del material ferroeléctrico que constituye la matriz.Peer reviewe

Field distribution near optical antennas at the subnanometric scale

This consistent and systematic review of recent advances in optical antenna theory and practice brings together leading experts in the fields of electrical engineering, nano-optics and nano-photonics, physical chemistry and nanofabrication. Fundamental concepts and functionalities relevant to optical antennas are explained, together with key principles for optical antenna modelling, design and characterisation. Recognising the tremendous potential of this technology, practical applications are also outlined. Presenting a clear translation of the concepts of radio antenna design, near-field optics and field-enhanced spectroscopy into optical antennas, this interdisciplinary book is an indispensable resource for researchers and graduate students in engineering, optics and photonics, physics and chemistryPeer Reviewe

Determinación de las propiedades ópticas en el infrarrojo de "gama"-Fe2O3

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Aplicada. Fecha de lectura: 20-01-199