Navegando por Autor "Pearson, J.E."
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Artigo Anomalous magnetoresistance in Fibonacci multilayers(American Physical Society, 2012-06-15) Bezerra, Claudionor Gomes; Machado, Leonardo Dantas; Corrêa, Marcio Assolin; Feitosa, Carlos Chesman de Araújo; Pearson, J.E.; Hoffman, A.We theoretically investigated magnetoresistance curves in quasiperiodic magnetic multilayers for two different growth directions, namely, [110] and [100]. We considered identical ferromagnetic layers separated by nonmagnetic layers with two different thicknesses chosen based on the Fibonacci sequence. Using parameters for Fe/Cr multilayers, four terms were included in our description of the magnetic energy: Zeeman, cubic anisotropy, bilinear coupling, and biquadratic coupling. The minimum energy was determined by the gradient method and the equilibrium magnetization directions found were used to calculate magnetoresistance curves. By choosing spacers with a thickness such that biquadratic coupling is stronger than bilinear coupling, unusual behaviors for the magnetoresistance were observed: (i) for the [110] case, there is a different behavior for structures based on even and odd Fibonacci generations, and, more interesting, (ii) for the [100] case, we found magnetic field ranges for which the magnetoresistance increases with magnetic fieldArtigo Static and dynamic properties of Fibonacci multilayers(AIP Publishing, 2013-03-06) Machado, Leonardo Dantas; Bezerra, Claudionor Gomes; Corrêa, Marcio Assolin; Feitosa, Carlos Chesman de Araújo; Pearson, J.E.; Hoffman, A.We theoretically investigate static and dynamic properties of quasiperiodic magnetic multilayers. We considered identical ferromagnetic layers separated by non-magnetic spacers with two different thicknesses chosen based on the Fibonacci sequence. Using parameters for Fe/Cr, the minimum energy was determined and the equilibrium magnetization directions found were used to calculate magnetoresistance curves. Regarding dynamic behavior, ferromagnetic resonance (FMR) curves were calculated using an approximation known from the literature. Our numerical results illustrate the effects of quasiperiodicity on the static and dynamic properties of these structures. We would like to thank the Brazilian Research Agencies CNPq, FINEP, FAPERN, and FAPESP for the financial support. Work at Argonne was supported by the US Department of Energy, Basic Energy Sciences under Contract No. DE-AC02-06CH1135. CGB acknowledges financial support from CAPES (Grant No 10144-12-9).