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Magnetism in low-dimensional systems: nanoparticles, nanowires and multilayer thin films

Grant number: 11/07117-5
Support Opportunities:Regular Research Grants
Duration: February 01, 2012 - January 31, 2014
Field of knowledge:Physical Sciences and Mathematics - Physics - Condensed Matter Physics
Principal Investigator:Daniel Reinaldo Cornejo
Grantee:Daniel Reinaldo Cornejo
Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil


In this research project we propose the study of magnetic phenomena in various materials characterized by the nanometric size of its basic components. Multilayers spin valves composed of magnetic metals or alloys (Fe, Co, NiFe), non-magnetic separators (Cu, Cr) and antiferromagnetic alloys (NiO, FeMn, IrMn) will be deposited via sputtering on Si or MgO subtracts. The aim is to prepare different sets of spin valves with different thicknesses of the magnetic layers, or the separators, or both, in order to study the effects of interactions between particles and also between the different layers. Special attention will be paid to the behavior of magnetoresistance and Hall effect, particularly in conditions of no saturation. First-order-reversal-curve (FORC) measures of magnetoresistance and Hall voltage will be obtained in these systems, and the corresponding distributions are calculated and interpreted using a new methodology FORC. We also propose the preparation via sputtering of thin films of Fe1-xRhx, Fe1-xRhx/Py, Fe1-xRhx/SmCo, and Fe1-xRhx/CoPd. The behavior of the antiferro-ferromagnetic phase transition of Fe1-xRhx, as a function of composition and thickness of the FeRh layer, will be studied. The possible transitions between exchange-bias and exchange-spring behavior, as well as the coercivity enhancement, will be studied in these heterogeneous films. The behavior of the perpendicular anisotropy showed by the Fe1-xRhx/Py films should be studied as a function of layer thickness and temperature.A comprehensive study of the behavior of magnetic nanoparticles and nanowires, diluted in thermotropic and lyotropic liquid crystals, should be carried out. The interest is to study and understand the influence of the anisotropy of chemically different liquid crystals (and even at different phases) on the magnetic behavior of magnetite nanoparticles, ferrite of cobalt, and nanowires of magnetic metals such as Ni and Co. In all cases, micromagnetic and phenomenological models should be developed in order to correlate theory and experiment. (AU)

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