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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]

A method to increase the relative cooling power to be used in Ericsson like refrigeration cycles is presented. The technique is based in the modification of the magnetic properties by the application of hydrostatic pressure on magnetic samples. The main advantage is to reach larger values of the magnetic entropy change in a wider temperature region (the so-called “table like” behavior). The study was carried out in a manganite belonging to the family of La 0.625−y Nd y Ca 0.375 MnO 3 , and some conclusions were compared with the expected behavior in other materials extracted from literature. [ABSTRACT FROM AUTHOR]

We report on the fabrication and characterization of La 2/3 Ca 1/3 MnO 3 manganite-based memristive devices. Polycrystalline manganite thin films were grown by Pulsed Laser Deposition, while metallic electrodes were deposited by sputtering. We show that, depending on the polarity of the initial electroforming, both clockwise and anti-clockwise current–voltage curves can be obtained. We attribute this behavior to the coexistence of different resistive switching mechanisms. We finally evaluate the electrical behavior of our devices after irradiation with high energy oxygen ions. We find no significant difference in the dielectric breakdown voltages between irradiated and non-irradiated devices, indicating that they may present radiation hardness and could be therefore appropriate for space or nuclear applications. [ABSTRACT FROM AUTHOR]

Abstract: A morphological and magnetic study of sub-micrometric nanostructures of a manganese oxide-based compound La0.325Pr0.300Ca0.375MnO3 is presented. Nanowires of 50 and 100nm and tubes with external diameters of 200 and 800nm were synthesized. Scanning electron microscopy with EDS microanalysis (SEM) and transmission electron microscopy (TEM) allowed to characterize the morphology and microstructure of these nanostructures. The walls of the nanotubes are composed of on average 40nm grain size particles, while in nanowires the grains are much smaller, in the range between 4 and 20nm. In both situations, the small grains present a random crystalline orientation, as it is confirmed by TEM diffraction experiments. Magnetization measurements and hysteresis loops are presented and discussed based on magnetic interaction between the grains, anisotropy considerations and reversal magnetization mechanisms. [Copyright &y& Elsevier]

Abstract: Magnetic properties of a single nanotube whose walls are constituted by nanograins of La2/3Sr1/3MnO3 are studied by means of Monte Carlo (MC) simulation. The system is considered as composed by ferromagnetic grains which couple via dipolar interaction. The grain size distribution is obtained from experimental measurements and the inter-grain distance distribution is obtained from a study of distance distribution among magnetic particles distributed in the tube walls. We show the magnetization behavior for a tube of 700nm of diameter and 3.5μm length. We discuss the simulation for different temperatures and external fields. As a main result, we show that the distribution of inter-granular distances has a unique behavior for tubular structures of similar diameter/length aspect ratio, independent of their sizes. This scaling relation allows us to perform the simulations using a tube of smaller dimensions. We succeed in explaining the magnetization curves, finding that dipolar interaction is necessary to explain the experimental behavior and that the grains behave as having magnetic dead layers. [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]