Angular-dependence of magnetization switching for a multi-domain dot: experiment and simulation

We have measured the in-plane angular variation of nucleation and annihilation fields of a multi-domain magnetic single dot with a microsquid. The dots are Fe/Mo(110) self-assembled in UHV, with sub-micron size and a hexagonal shape. The angular variations were quantitatively reproduced by micromagnetic simulations. Discontinuities in the variations are observed, and shown to result from bifurcations related to the interplay of the non-uniform magnetization state with the shape of the dot.Comment: 4 pages, 4 figures, for submission as a regular articl

Magnetic domain walls in constrained geometries

Magnetic domain walls have been studied in micrometer-sized Fe20Ni80 elements containing geometrical constrictions by spin-polarized scanning electron microscopy and numerical simulations. By controlling the constriction dimensions, the wall width can be tailored and the wall type modified. In particular, the width of a 180 degree Neel wall can be strongly reduced or increased by the constriction geometry compared with the wall in unconstrained systems.Comment: 4 pages, 6 figure

Growth modes of Fe(110) revisited: a contribution of self-assembly to magnetic materials

We have revisited the epitaxial growth modes of Fe on W(110) and Mo(110), and propose an overview or our contribution to the field. We show that the Stranski-Krastanov growth mode, recognized for a long time in these systems, is in fact characterized by a bimodal distribution of islands for growth temperature in the range 250-700°C. We observe firstly compact islands whose shape is determined by Wulff-Kaischev's theorem, secondly thin and flat islands that display a preferred height, ie independant from nominal thickness and deposition procedure (1.4nm for Mo, and 5.5nm for W on the average). We used this effect to fabricate self-organized arrays of nanometers-thick stripes by step decoration. Self-assembled nano-ties are also obtained for nucleation of the flat islands on Mo at fairly high temperature, ie 800°C. Finally, using interfacial layers and solid solutions we separate two effects on the preferred height, first that of the interfacial energy, second that of the continuously-varying lattice parameter of the growth surface.Comment: 49 pages. Invited topical review for J. Phys.: Condens. Matte

Potensi Pertumbuhan Ekonomi Kota Bitung

Regional development is an integral part of national development one of benchmart for regional devel-opment is regional economic know previously the potential of a region that can be develop optimally. The asms of this study to determine the potential of the region has major effect of economic growth in Bitung cluring 2010 to 2013, and contribution of economic sector to economic growth in Bitung. This study used PDRB data Bitung City and North Sulawesi Province from 2010 to 2013. Data were obtained from the relevant agencies. Data ana-lyted using LQ analysis. The result showed that sector has LQ > 1 is processing Industry with average LQ 2,84 %, electricity, gas and pure water sector with average LQ 2,22 %, Transportasion and Communications sector with average LQ 1,82 % and Agriculture sector with average LQ 1,07 %. From the four sector showed that the four basic sector has economic strength and influence to increase economic growth in Bitung and this sector has been able to infest the needs of their own region. The industrial sector development as a basic sector, suggested to used local raw industrial, efficient and competitive and directed the development of Agriculture and fisheries industry, improving quality and economics product. The fourth development of the base sectors namely manufac-turing, electricity, gas and water supply, transport and communications and agriculture sector without neglecting the development of the non base which also has the potential for the sector is developed as the financial, real es-tate and business services sector and the services sector expected to be able to increase the rate of economic growth Bitung

Direct observation of domain-wall configurations transformed by spin currents

Direct observations of current-induced domain-wall propagation by spin-polarized scanning electron microscopy are reported. Current pulses move head-to-head as well as tail-to-tail walls in sub-micrometer Fe_{20}Ni_{80} wires in the direction of the electron flow, and a decay of the wall velocity with the number of injected current pulses is observed. High-resolution images of the domain walls reveal that the wall spin structure is transformed from a vortex to a transverse configuration with subsequent pulse injections. The change in spin structure is directly correlated with the decay of the velocity.Comment: 5 pages, 3 figure

Three-dimensional magnetic flux-closure patterns in mesoscopic Fe islands

We have investigated three-dimensional magnetization structures in numerous mesoscopic Fe/Mo(110) islands by means of x-ray magnetic circular dichroism combined with photoemission electron microscopy (XMCD-PEEM). The particles are epitaxial islands with an elongated hexagonal shape with length of up to 2.5 micrometer and thickness of up to 250 nm. The XMCD-PEEM studies reveal asymmetric magnetization distributions at the surface of these particles. Micromagnetic simulations are in excellent agreement with the observed magnetic structures and provide information on the internal structure of the magnetization which is not accessible in the experiment. It is shown that the magnetization is influenced mostly by the particle size and thickness rather than by the details of its shape. Hence, these hexagonal samples can be regarded as model systems for the study of the magnetization in thick, mesoscopic ferromagnets.Comment: 12 pages, 11 figure

Experiencias sencillas aplicando conceptos básicos de Termodinámica

Es conocido el hecho que la Termodinámica es una unidad temática dentro de la currícula del tercer año del Polimodal, como así también dentro de las asignaturas correspondientes a la mayoría de las carreras de Ingeniería y Ciencias Exactas. En base a las experiencias realizadas con diferentes grupos de alumnos de distintas carreras y niveles, se pudo observar que ciertos conceptos termodinámicos, tales como, energía, calor, trabajo, entalpía, procesos endo y exotérmicos, entre otros, no llegan a ser comprendidos en su totalidad por los mismos, ya que involucran un lenguaje abstracto y su comprensión, en general, está basada en exposiciones teóricas y resolución de problemas, con pocas actividades prácticas. En todos los niveles educativos existe la tendencia a mejorar las estrategias de enseñanza- aprendizaje tradicionales, donde el docente expone los conocimientos y los alumnos son los receptores pasivos de los mismos. En la búsqueda de otras alternativas de comprensión y participación, en las que los alumnos puedan desarrollar habilidades de observación fenomenológica, análisis, justificación de los mismos aplicando los conocimientos previamente adquiridos y logrando su contextualización, se desarrollan tres actividades: “Fuego sin fuego”, “Congelamiento del agua”y “Ensayo cuantitativo: Determinación del calor de neutralización”. A través de éstas se pretende, que el alumno tome una posición reflexiva y crítica, y además promueva su expresión oral y escrita, elaborando informes de carácter técnico, desarrollando capacidades de argumentación y justificación de las propias opiniones.Sección NaturalesDepartamento de Ciencias Exactas y Naturale

Classical behavior of deformed sine-Gordon models

In this work we deform the phi^4 model with distinct deformation functions, to propose a diversity of sine-Gordon-like models. We investigate the proposed models and we obtain all the topological solutions they engender. In particular, we introduce non-polynomial potentials which support some exotic two-kink solutions.Comment: 12 pages, 12 figures; version to appear in Physica

Lichen planus and Hepatitis C: a case-control study

BACKGROUND: The association of lichen planus with hepatitis C (HCV) has been widely reported in the literature. However, there are wide geographical variations in the reported prevalence of HCV infection in patients with lichen planus. This study was conducted to determine the frequency of hepatitis C in Iranian patients with lichen planus at Razi hospital, Tehran. METHODS: During the years 1997 and 1998, 146 cases of lichen planus, 78 (53.1%) women and 69 (46.9%) men were diagnosed. They were diagnosed on the basis of the usual clinical features and, if necessary, typical histological findings. The patients were screened for the presence of anti-HCV antibodies by third generation ELISA and liver function tests. We used the results from screening of blood donors for anti HCV (carried out by Iranian Blood Transfusion Organization) for comparison as the control group. RESULTS: Anti-HCV antibodies were detected in seven cases (4.8%). This was significantly higher than that of the blood donors' antibodies (p < 0.001). The odds ratio was 50.37(21.45–112.24). A statistically significant association was demonstrated between erosive lichen planus and HCV infection. Liver function tests were not significantly different between HCV infected and non-infected patients. CONCLUSION: HCV apears to have an etiologic role for lichen planus in Iranian patients. On the other hand, liver function tests are not good screening means for HCV infection