GERENCIA DE ÁREA INVESTIGACIÓN, DESARROLLO E INNOVACIÓN (GAIDI)
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Ítem Solo Metadatos Influence of argon pressure on the structural properties of polycrystalline sputtered Fe0.89Ga0.11 thin films(AIP Publishing, 01-01-2021) Ramírez,G.A.; Moya-Riffo,A.; Gómez,J.E.; Malamud,F.; Rodríguez,L.M.; Fregenal,D.; Bernardi,G.; Butera,A.; Milano,J.In this work, we present a systematic study on the relation between the elastic behavior and the structural properties of polycrystalline Fe0.89Ga0.11 thin films deposited on Si(100) substrates. By carrying out pole figure (PF) measurements, we determined the evolution of the texture components, residual stress and Young's modulus (Ys) as a function of the Ar pressure. The samples display several fiber-like texture components (where the fiber axes is always along the growth direction) beside to a random component; the texture component weights depend on the Ar pressure. The study of the residual stress reveals that the samples present a tensile stress, that relaxes when the Ar pressure increases. In the case of Ys, the estimated values vary slightly within the Ar pressure range studied. Finally, the residual stress and Ys behavior is correlated with the microstructure evolution by using the orientation distribution function (ODF) simulated from the PFs.Ítem Solo Metadatos Silica-collagen nanoformulations with extended human growth hormone release(Purpose-Led Publishing, 01-02-2023) Villarruel, Luis A.; Brie, Belén; Municoy, Sofía; Becú-Villalobos, Damasia; Desimone, Martín F.; Catalano, Paolo N.Growth hormone deficiency has been treated by the daily administration of recombinant human growth hormone (hGH) for decades. Patient compliance to this treatment is generally incomplete due to challenges including dose frequency and lack of perceived benefits. This stimulates the research on new formulations to reduce the number of periodic administrations. In this study silica nanoparticles and silica-collagen nanocomposites were evaluated for hGH loading and release. Bare nanoparticles showed higher hGH adsorption capacity than thiol- and isobutyl-bearing particles of similar diameters. Monitoring of bound protein conformation changes indicated hGH structure retention when adsorbed on bare silica nanoparticles and suggested no alterations on protein activity. Protein-loaded particles incorporated into collagen matrices (silica-collagen nanocomposites) showed a progressive protein release profile different from the observed for hGH-loaded silica nanoparticles and hGH-loaded collagen matrices. While both the collagen and the silica nanoparticle systems reached a 100 % release after 4 and 7 days respectively, silica-collagen nanocomposites showed a bi-phasic prolonged hGH release reaching approximately an 80 % after 15 days. These findings suggest that biocompatible silica-collagen nanocomposites could be used as vehicles for the prolonged delivery of hGH which could lead to a potential reduction in the number of periodic administrations.Ítem Solo Metadatos Coexistence of volatile and nonvolatile memristive effects in phase-separated La0.5Ca0.5MnO3-based devices(Elsevier, 06-02-2023) Ramírez, G. A.; Román Acevedo, W.; Rengifo, M.; Nuñez, J. M.; Aguirre, M. H.; Briático,J.; Rubi,D.In this work, we have investigated the coexistence of volatile and nonvolatile memristive effects in epitaxial phase-separated La0.5Ca0.5MnO3 thin films. At low temperatures (50 K), we observed volatile resistive changes arising from self-heating effects in the vicinity of a metal-to-insulator transition. At higher temperatures (140 and 200 K), we measured a combination of volatile and nonvolatile effects arising from the synergy between self-heating effects and ferromagnetic-metallic phase growth induced by an external electrical field. The results reported here add phase separated manganites to the list of materials that can electrically mimic, on the same device, the behavior of both neurons and synapses, a feature that might be useful for the development of neuromorphic computing hardware.Ítem Acceso Abierto 4D Printing: The Development of Responsive Materials Using 3D-Printing Technology(MDPI, 07-12-2023) Antezana, Pablo Edmundo; Municoy, Sofia; Ostapchuk, Gabriel; Catalano, Paolo Nicolás; Hardy, John G.; Evelson, Pablo A.; Orive, Gorka; Desimone, Martin FedericoAdditive manufacturing, widely known as 3D printing, has revolutionized the production of biomaterials. While conventional 3D-printed structures are perceived as static, 4D printing introduces the ability to fabricate materials capable of self-transforming their configuration or function over time in response to external stimuli such as temperature, light, or electric field. This transformative technology has garnered significant attention in the field of biomedical engineering due to its potential to address limitations associated with traditional therapies. Here, we delve into an in-depth review of 4D-printing systems, exploring their diverse biomedical applications and meticulously evaluating their advantages and disadvantages. We emphasize the novelty of this review paper by highlighting the latest advancements and emerging trends in 4D-printing technology, particularly in the context of biomedical applications.Ítem Acceso Abierto Microcavity phonoritons – a coherent optical-to-microwave interface(Springer Nature, 18-09-2023) Kuznetsov, Alexander Sergeevich; Biermann, Klaus; Reynoso, Andres Alejandro; Fainstein, Alejandro; Santos, Paulo VenturaOptomechanical systems provide a pathway for the bidirectional optical-to-microwave interconversion in (quantum) networks. These systems can be implemented using hybrid platforms, which efficiently couple optical photons and microwaves via intermediate agents, e.g. phonons. Semiconductor exciton-polariton microcavities operating in the strong light-matter coupling regime offer enhanced coupling of near-infrared photons to GHz phonons via excitons. Furthermore, a new coherent phonon-exciton-photon quasiparticle termed phonoriton, has been theoretically predicted to emerge in microcavities, but so far has eluded observation. Here, we experimentally demonstrate phonoritons, when two exciton-polariton condensates confined in a μm-sized trap within a phonon-photon microcavity are strongly coupled to a confined phonon which is resonant with the energy separation between the condensates. We realize control of phonoritons by piezoelectrically generated phonons and resonant photons. Our findings are corroborated by quantitative models. Thus, we establish zero-dimensional phonoritons as a coherent microwave-to-optical interface.Ítem Solo Metadatos Magnetization reversal modes and coercive field dependence on perpendicular magnetic anisotropy in FePt thin films(Purpose-Led Publishing, 30-06-2023) Román, A.; Lopez Pedroso, A.; Bouzehouane, K.; Gómez, J.E.; Butera, A.; Aguirre, M.H; Medeiros Soares, M.; García, C.; Steren, L.B.The competition between shape and perpendicular magnetic anisotropies in magnetic thin films gives rise to unusual magnetic behaviors. In ferromagnetic thin films, the presence of an out-of-plane component of the magnetic anisotropy may induce a transition from planar to stripe-like magnetic domains above a critical thickness. In this article, we present a detailed study of the magnetization switching mechanism in FePt thin films, where this phenomenon is observed. Using micromagnetic simulations and experiments, we found that below the reversal mechanism is well described by the two-phase model while above this thickness the magnetization within each stripe reverses by coherent rotation. We also analyzed the out-of-plane component of the magnetic anisotropy and its temperature dependence, probing that substrate-induced strains are responsible for the abnormal coercive field behavior observed for FePt films.Ítem Acceso Abierto Longitudinal Magnetomorphic Effect in Indium Films(American Physical Society, 1967-11-15) de la Cruz, F.; de la Cruz, M.E.; Cotignola, J.M.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasMeasurements of magnetomorphic effects in indium films of thickness between 0.003 and 0.01 cm have been made at 4.2 and 1.5°K. The results were compared with theoretical calculations based on the free-electron model. To make these comparisons, it was necessary to discount the bulk magnetoresistance by means of a modified Kohler's rule suggested by Olsen. From the comparison of the data with the theory, it was possible to deduce the values of the electronic momentum mv and the product of the bulk resistivity with the bulk mean free path ρbl. Data previously obtained by Olsen in wires have been analyzed with the use of measurements of Kohler's rule and of a criterion for the comparison different from the one used by Olsen. The experimental value of ρbl is discussed on the basis of an analysis made by Bate et al., in which the anisotropy of the mean free path is taken into account.Ítem Acceso Abierto Thermal and Electrical Conductivities of Very-High-Purity Indium(American Physical Society, 1968-12-00) de la Cruz, M.E.; Cotignola, J.M.; Bressan, O.J.; Luengo, C.A.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasMeasurements of the thermal and electrical conductivities of a polycrystalline indium sample of very high purity have been performed between 1.5 and 4.2°K and in the presence of longitudinal magnetic fields up to 15 000 Oe. It was found that, within the experimental error, the electrical and thermal Kohler's rules were satisfied, the functional forms for the two being quite similar. The expression for the resistivity as a function of T for the normal state and in zero magnetic field are in good agreement with theory. The Lorenz number obtained by extrapolating to T=0 gives a very high value compared with the theoretical one. Measurements of the thermal conductivity for the superconducting state, in the same temperature range, have been made. The thermal-resistivity ratio WnWs as a function of the reduced temperature does not agree with the results of Kadanoff and Martin.Ítem Acceso Abierto Experimental Heat Capacity of Pure Liquid He3(American Physical Society, 1969-09-00) Mota, A.C.; Platzeck, R.P.; Rapp, R.; Wheatley, J.C.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasMeasurements of the heat capacity of pure He3 at 0.24 atm obtained by a differencing method are presented for the temperature range from 20-150 m°K. The temperature scale T∗ used is that valid for powdered cerium magnesium nitrate in the form of a right circular cylinder with diameter equal to height. There is excellent agreement between the present and earlier measurements. Considering all low-pressure difference data we find that from 6-125 m°K the ratio of heat capacity to magnetic temperature decreases linearly with increasing temperature. The relationship of the measurements to the temperature scale and to theories of spin fluctuations in He3 is also discussed.Ítem Acceso Abierto Variation of the Ratio Hc3/Hc2 in the Immediate Vicinity of Tc(American Physical Society, 1969-11-10) de la Cruz, F.; Maloney, M.D.; Cardona, M.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasWe have measured the ratio Hc3Hc2 for tin-rich Sn-In alloys and for indium-rich In-Bi alloys in the immediate vicinity of Tc. For the Sn-In system this ratio decreases as Tc is approached. Similar behavior has been recently reported by Ostenson and Finnemore for pure Nb. The In-Bi alloys, however, show a marked increase in Hc3Hc2 as the critical temperature is approached.Ítem Acceso Abierto Low-Temperature Specific Heats of the beta and zeta Phases in Equiatomic AgZn(American Physical Society, 1970-09-15) Abriata, J. P.; Bressan, O. J.; Luengo, C. A.; Thoulouze, D.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasHeat-capacity measurements between 1.3 and 4.2°K have been made on equiatomic AgZn in both the β′ and ζ0 phases. Significant differences were found in the Debye temperature and the electronic specific-heat coefficient, the latter data being discussed in terms of Fermi-surface-Brillouin-zone interactions. Furthermore, it is concluded that β′ is the stable phase at 0°K, and that in this particular alloy, vibrational properties are of major importance in controlling phase stability near 0°K.Ítem Acceso Abierto Anomalous Behavior of Hc3/Hc2 near Tc for Sn-In and In-Bi Alloy Systems(American Physical Society, 1970-10-01) Maloney, M.D.; de la Cruz, F.; Cardona, M.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasPreviously reported measurements of the ratio Hc3Hc2 for tin-rich Sn-In alloys and indium-rich In-Bi alloys have been extended in further detail, and include variations in foil thickness (6 - 300 μ). The anomalous behavior in the ratio very near Tc is found to be dependent on foil thickness. Each alloy system is characterized by a certain thickness, above which Hc3Hc2 decreases markedly as Tc is approached, and below which the opposite behavior takes place. The results can be interpreted qualitatively in terms of a sandwich model in which the strength of the pairing interaction is depressed in a layer at the surface of the sample. For the thickest samples (most nearly "semi-infinite"), there is good quantitative agreement with the recent theory of this proximity effect given by Fink and Presson.Ítem Acceso Abierto Superconductive Supercooling and Superheating of Small Cadmium Spheres: Size Effects(American Physical Society, 1971-06-01) de la Cruz, F.; Maloney, M.D.; Cardona, M.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasSupercooling and superheating have been observed for samples composed of small cadmium spheres of uniform well-defined sizes. The data obtained for large sphere diameters are independent of size and represent, by all indications, ideal bulk properties. The supercooling data for such spheres have been used to obtain the Ginsburg-Landau parameter κ and, in conjunction with BCS expressions, the penetration depth λ and the coherence length ξ0. The temperature dependence of the supercooling field Hsc shows an anomaly for t∼0.8, very similar to that previously reported for Al and Zn. The superheating field of these "bulk" spheres shows strong effects of the nonlocal electrodynamics below Tc. Spheres of diamters equal to or smaller than 10 μ show strong size effects in the supercooling and superheating fields, especially near Tc. The results are examined in the light of existing theories of critical fields for small spheres. A systematic decrease of the critical temperature with sphere size has also been observed. It seems related to a decrease in the gap anisotropy, produced by boundary scattering. These results are analyzed in terms of the theory of Markowitz and Kadanoff.Ítem Acceso Abierto Superconducting Parameters and Size Effects of Aluminum Films and Foils(American Physical Society, 1972-05-01) Maloney, M.D.; de la Cruz, F.; Cardona, M.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasIn this paper we present the experimental results and analysis of the critical-field determination of aluminum films and foils. We studied the thermodynamic parallel and perpendicular critical fields as a function of thickness and temperature. The measurement of the critical fields together with suitable theories allows the determination of the penetration depth λ, the coherence length ξ, and the surface-energy parameter Δ. The thermodynamic transition of all films studied was of second order. Measurement in both magnetic field orientations offers a check on the consistency of the methods used to analyze the data. The value of the Ginzburg-Landau parameter κ obtained from these measurements is six times larger than the value obtained from supercooling experiments. This phenomenon has been observed previously by other authors in different metals. The superconducting transition of all foil samples was of first order. In perpendicular fields the transition to the intermediate state was analyzed by means of an interpolation formula having the correct theoretical behavior in the limits of both large and small thicknesses. The value of the surface-energy parameter so obtained is in agreement with the supercooling result.Ítem Acceso Abierto Low angle electron scattering in thermal resistivity(IOP Publishing, 1975-00-00) Bressan, O.J.; Ridner, A.E.; de la Cruz, F.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasElectrical ( rho ) and thermal (W) resistivity measurements in very dilute In alloys between 1K and 4K show a temperature dependence expressed by rho = rho 0+ beta T5 and WT=(WT)0+AT3+BT5. The BT5 term in the thermal resistivity is due to a contribution from a 'diffusion-like process' of electrons over the Fermi surface, as is the one that describes the temperature dependence of the electrical resistivity. This claim is supported by the experimental fact that the Lorenz number defined as L= beta /B coincides with the value given by L= rho 0/(WT)0 which in turn agrees with the free electron value within 15%.Ítem Acceso Abierto T5 law and Matthiessen's rule(IOP Publishing, 1975-00-00) Bressan, O.J.; Ridner, A.E.; de la Cruz, F.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasPrecise electrical resistivity measurements on very dilute non magnetic indium alloys show no doubt in a T5 dependence on temperature between 1-4K and strong deviations from Matthiessen rule. Measurements of thermal resistivity show that the extrapolation method to obtain the data to H=0 is correct. Comparison of the results with recent theories is discussed.Ítem Acceso Abierto Surface-Temperature Determination in the Kapitza Problem(American Physical Society, 1975-09-29) Ridner, A.; Martínez, E. N.; de la Cruz, F.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasIt is shown that surface superconductivity can be used as a localized thermometer. Its application to the study of the thermal boundary resistance at a Pb-4He interface provides the first experimental evidence for the existence of a rapid temperature variation within microscopic distances from the surface.Ítem Acceso Abierto Low temperature specific heat of Th-Gd spin glass(Elsevier, 1979-03-00) Sereni, J.G.; Huber, T.E.; Luengo, C.A.The specific heat measurements of T-Gd alloys, with Gd concentration ranging from 0.15% to 10.8% and temperatures between 0.4 and 8 K, are reported. The characteristic spin glass specific heat enhancement and its maximum was found linearly proportional to Gd concentration. At low temperatures a T2 dependence of the specific heat was observed and the entropy associated with the magnetic ordering was the 70% of the expected value for the spin S=72.Ítem Acceso Abierto Interconfigurational fluctuations in Ce cubic compounds(EDP Sciences, 1979-05-00) Sereni, J.G.; Olcese, G.L.; Rizzuto, C.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasThe magnetic susceptibility of thirty Ce cubic compounds is analyzed, assuming a temperature dependence of the valence fluctuations. The energy level scheme, obtained by fitting the measured susceptibility is used to calculate other physical properties. A correlation between the Ce ionic radius and the interconfigurational excitation energy has been found.Ítem Acceso Abierto Temperature dependence of the superconducting giant-vortex state. Theory and Experiment(American Physical Society, 1979-09-01) de la Cruz, F.; Fink, H.J.; Luzuriaga, J.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasWhen a type-I superconductor with a surface nucleation field Hc3(T)>Hc(T) (thermodynamic critical field) is thermally cycled in an axially applied magnetic field H0 between the temperatures T(Hc3) and about T(Hc), experiments show that the magnetization changes reversibly. The latter is diamagnetic near T(Hc3) but can be paramagnetic just above T(Hc). This behavior is explained by assuming that the fluxoid quantum number b is fixed at the transition from the normal to the superconducting state and retained at lower temperatures. The value of b is determined almost entirely by the flux at the transition which is enclosed by a contour located at a distance ξ1.7 from the surface inside the cylinder (ξ is the coherence length). The temperature variation of the order parameter f at the surface of the cylinder, the magnetization m, and the temperature at which m=0 for f≠0 are calculated for R≫ξ. Conservation of the fluxoid quantum number, while T is varied causes the two opposing surface currents to become imbalanced. This is the source of the observed para- and diamagnetism.