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Physical properties of La0.8Sr0.2MnO3 nanotubes and fibers Daniel Felipe Simião1, Alessandra Zenatti1 and Marcia T. Escote1 1

Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas (CECS), Universidade Federal do ABC (UFABC), Av. dos Estados, 5001, Bairro Bangu, Santo André, SP, Brazil ABSTRACT

This work describes the study of synthesis and physical characterization of nanostructured manganite oxides. The La0.8Sr0.2MnO3 (LSM) nanotubes and fibers have been prepared by electrospinning and pore wetting technique. The samples were characterized by Xray diffraction (XRD), scanning electron microscopy (SEM) and magnetization as a function of temperature (M(T)). XRD results of LSM fibers and nanotubes revealed that both samples crystallize in a rhombohedra-distorted perovskite structure. SEM pictures of these samples revealed ultrafine grains assembled in fibers and nanotubes samples. Analysis of these images revealed samples with external diameter ranging from 300 to 1.4 mm, and 7 µm to hundreds of mm in length. The M(T) measurements of samples La0.8Sr0.2MnO3 revealed a paramagnetic/ferromagnetic transition with decreasing temperature. Such transition occurs at temperatures of Tc ≈ 337 K and Tc ≈ 360 K for the nanotubes and fibers, respectively. Furthermore, this variation of the Tc values is also reported in literature for other manganite nanostructures. Such variation can be related to the microstructural characteristics observed for both LSM samples produced in this work. In general, it is believed that both methodologies allowed the production of nanostructures LSM. Also, these results suggest that the dimensionality of the samples seems to interfere in the physical properties of LSM manganite. INTRODUCTION Low dimensional nanostructured materials have attracted considerable attention in the last decades; it is due to their unique properties and possible applications. In particular, nanoparticle, nanowires and nanotubes of carbon, metals, oxides, semiconductors and polymers have been reported [1-7]. Also, the recent development of several synthesis methods for manganite nanostructures opened a wide range of possible applications [8-13]. It can be cited the future applications in ultra-high-density magnetic recording media [9,10] and electronic devices [11], magneto-electronics, bolometric infrared detectors and solid oxide fuel cells [1215] In these sense, several compositions of nanostructures manganites have been synthesized as, for example, Pr0.5Sr0.5MnO3 nanowires [16] and La0.325Pr0.300Ca0.725MnO3 [4,6], La0.25Ca0.75MnO3 [17] and La0.67Sr0.33MnO3 nanotubes [5] by different procedures. Some of these works describe the synthesis of manganite nanotubes and nanowires by template assisted method and they describe the correlation between the size of these nanostructures and their magnetic properties. Also, high quality La0.67Sr0.33MnO3 [5] and La0.8Sr0.2MnO3 [15] fibers with varying diameters have been grown by electrospinning process. The investigation of the magnetotransport of these LSM fibers indicates tha