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Growth and study of magnetic nanostructures.


The visit of Dr. Waldemar Macedo, from the Center for the Development of Nuclear Technology (CDTN), at the Laboratory of Materials and Low Temperatures (LMBT) of the State University of Campinas (UNICAMP), aims to allow the addition of a specialist on sinthesis and characterization of nanostructured magnetic materials, specially ultrathin films and multilayers, epitaxial or not, and on the structure - magnetism correlations, in two current projects financed by FAPESP: the thematic project Emerging phenomena in reduced size systems, as well as an international cooperation project with the University of Porto, Dimensionality effects on the physical properties of magnetostrictive and Heusler type intermetallic materials: 1 to 3 dimensions architectures.Both projects involve the growth of intermetallic nanowires using templates of nanoporous alumina, of compounds for which the crystalline structure quality is imperative. The currently used technique is called nanonucleation via metal flux and was patented by the LMBT itself. It consists of the combination of the growth method of intermetallic alloys by metallic flux and the use of nanoporous alumina membrane as template to obtain nanowires. Unlike bulk material growth, nanowire growth is strongly influenced by the pore surface and may be associated to a liquid phase epitaxial process. As a consequence, growth control depends on several factors similar to those important during gas phase epitaxial growth (surface state, crystalline structure of the surface and material to be grown, etc.). In this sense, Dr. Macedo's extensive experience in these aspects will allow us to understand and optimize the phenomena related to epitaxial growth during the fabrication of intermetallic nanowires by nanonucleation via metallic flux. This help will accelerate the growth parameter adjustment for materials with new compositions.Within the intermetallic alloys, the Heusler family presents many interesting properties, especially for spintronic applications. Both projects related to Dr. Macedo's visit have objectives of achieving the fabrication of Heusler alloy nanowire. However, obtaining nanowires of the desired phase and of good crystalline quality (an essential feature) is hampered by being ternary compounds. One recognized technique for growing epitaxial thin films of Heusler alloys, including the families identified in the related projects, is Molecular Beam Epitaxy (MBE), in which Dr. Macedo is a specialist. In this context, we will take advantage of his visit to try to develop a new technique of fabricating magnetic nanowires, combining the MBE and alumina templates, and explore the possibilities for Heusler alloys.In summary, the current projects developed at UNICAMP's Laboratory of Materials and Low Temperatures (LMBT) will have an important boost with the addition of Dr. Waldemar Macedo to their participants, as epitaxial growth specialist, and more specifically via MBE and sputtering, directly involved in the experimental manipulations and result analysis. (AU)

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