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Hollow nanostructured spheres of Co, Zn, Mn and Ni ferrites were synthesized from metallic impregnation in situ during the formation of colloidal carbon microspheres from hydrothermal treatment of a glucose solution at 160 °C for 24h and then calcinated in air at 550 °C for 2h. The X-ray diffraction powder patterns reveal the formation of spinel-like crystalline ferrites as single phase, except for Zn derivative, which is observed the formation of ZnO additionally. The characterization by Scanning Electronic Microscopy and Transmission Electronic Microscopy showed that resulting solids consist of welldefined hollow microspheres with a external diameter size distribution between 0.4 ≤ de ≤ 8.1 μm. The Ferromagnetic Resonance (FMR) shows the characteristic Superparamagnetic behaviour of the nanoparticles that conform the microstructures of the spheres. In the ZnFe2O4 sample there are two FMR signals, the low field signal is attributed to the Superparamagnetic behaviour and the high field signal belongs together with a ferromagnetic attributable transition to ZnO, in agreement with that observed by X-ray diffraction. The CoFe2O4 shows a hysteresis loop characteristic of ferromagnetic order. [ABSTRACT FROM AUTHOR]

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In this study, presents the results of structural properties obtained by DRX, SEM and Mössbauer spectrocopy of the alloys systems FexMn0.6-xAl0.4 at 40% Al, obtained by mechanically alloying, with 48h alloying time. It was observed that the alloys consolidated in a bcc phase with a lattice parameter in according with that waited for this phase. The alloys show that powders initials Fe, Mn and Al are distributes uniform in the superface according the previous consolidated. Experimental results obtained at room temperatura by Mössbauer spectroscopy show that a paramagnetic phase for x < 0.4 and for range 0.45 ≥ x ≥ 0.6 a magnetic phase ordened. [ABSTRACT FROM AUTHOR]

Luttinger liquids are paramagnetic one-dimensional metals. The elementary excitations are collective charge and spin modes. The bosonization technique shows that all physical properties depend on three parameters: the renormalized coupling constant K and the charge and spin velocities. The theoretical correlation functions have behavior power law, the exponents depend on the interaction. We calculated Green's function and obtained the local density of states and momentum distribution. [ABSTRACT FROM AUTHOR]

Polycrystalline materials of La0.5Ba0.5MnO3 were prepared by the solid--state reaction method. The X--ray diffractogram showed an orthorhombic crystalline structure with parameters of a =5.59663 Å, b =7.80063 Å, c =5.53063 Å; with a probe vacuum microscope in magnetic force mode (MFM), to the surface of the compressed composite in cylindrical form, showed the presence of magnetic domains in the paramagnetic phase (PM), The overage magnetic interaction among the cantilever of the microscope and the domains is of the order 8.65 *10-2 nN. While the overage width of the domains was about 1.60µm. Calorimetric measures done with differential scanning calorimetric (DSC) showed a small anomaly in the heating flow in function of the temperature, which is associated to the transition temperature of the para-ferromagnetic phase. [ABSTRACT FROM AUTHOR]