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Abstract: We have measured the electrical resistance of micrometric to nanometric powders of the (LPCMO with ) manganite for hydrostatic pressures up to 4kbar. By applying different final thermal treatments to samples synthesized by a microwave assisted denitration process, we obtained two particular grain characteristic dimensions (40nm and 1000nm) which allowed us to analyze the grain size sensitivity of the electrical conduction properties of both the metal electrode interface with manganite (Pt/LPCMO) and the intrinsic intergranular interfaces formed by the LPCMO powder, conglomerate under the only effect of external pressure. We also analyzed the effects of pressure on the phase diagram of these powders. Our results indicate that different magnetic phases coexist at low temperatures and that the electrical transport properties are related to the intrinsic interfaces, as we observe evidences of a granular behavior and an electronic transport dominated by the Space Charge limited Current mechanism. [Copyright &y& Elsevier]

Abstract: Nanoparticles assembled into nanostructures (NAN) of manganese perovskite oxides for different compositions and diameters have been synthesized following a template-assisted method. We discuss the relationship among geometrical, structural and nanostructural parameters observed when synthesizing LaMnO3, La0.66Sr0.33MnO3, La0.66Ca0.33MnO3 and La0.325Pr0.300Ca0.375MnO3 manganite based complex oxides. For all the studied compounds, the structures are composed of an assembly of small (some few tens of nanometers) grains. They form nanotubes above some threshold diameter of the template, and nanowires below it. Here we focus on the correlation between grain size and the diameter at which the tube to wire crossover occurs. The threshold for this tube to wall crossover seems to depend on the specific compound. We present evidence from TEM observations that allow a rationalization of several phenomena in the synthesis process. [Copyright &y& Elsevier]

Abstract: Iron oxide–silica nanocomposite aerogels were produced by sol–gel procedure followed by the hypercritical evaporation of the solvent. Aerogels hosting maghemite were synthesized from the precursors TEOS and TMOS. Mean oxide particle size seems to be strongly influenced by the solvent. The magnetic properties of the iron oxide particles hosted in silica aerogeles pores were studied by means of magnetometry and AC susceptometry. Interrelation between synthesis parameters, structure and magnetic behavior is discussed. [Copyright &y& Elsevier]

Abstract: We have measured the pressure sensitivity of magnetic properties on nanostructured powders. Samples were synthesized following a microwave assisted denitration process and a final heat treatment at different temperatures to control the grain size of the samples. A span in grain diameters from 40nm to was obtained. Magnetization curves as a function of temperature were measured following different thermomagnetic histories. AC susceptibility as a function of temperature was also measured at different hydrostatic pressures (up to 10kbar) and for different frequencies. Our results indicate that the nanostructuration plays a role of an internal pressure, producing a structural deformation with similar effects to those obtained under an external hydrostatic pressure. [Copyright &y& Elsevier]

Abstract: We have developed a model that describes the ferromagnetic resonance spectra recently observed in nanotubes formed by assembled La0.67Sr0.33MnO3 manganite nanoparticles. The resonance line shape in these tubes resembles that of a system of randomly oriented flat particles instead of what is usually seen in elongated samples. In order to explain the experimental data we have assumed that each individual grain (or small group of grains) has an easy plane effective anisotropy which could be partially aligned in a cylindrical symmetry. The magnetization of each grain is also distributed around a mean value, and hence the magnitude of the anisotropy varies from grain to grain. Within this framework we have been able to fit reasonably well the resonance field and the overall line shape of nanotubes that were deposited on a glass substrate and were aligned in a magnetic field. From the simulations we have deduced an average effective magnetization with a distribution width of . This value of magnetization is smaller than that of bulk LaSr manganites at room temperature, probably due to the granular nature of the tubes. [Copyright &y& Elsevier]