458 research outputs found
Long-range order on the atomic scale induced at CoFeB/MgO interfaces
No full textEilers G, Ulrichs H, Muenzenberg M, Thomas A, Thiel K, Seibt M. Long-range order on the atomic scale induced at CoFeB/MgO interfaces. JOURNAL OF APPLIED PHYSICS. 2009;105(7):073701.The amorphous (a-) CoFeB/crystalline (c-) MgO based tunneling system interface has been studied by means of quantitative high resolution transmission electron microscopy from atomic to micrometer length scales with increasing annealing temperatures. On the micron scale an irregular nucleation is found. On the atomic scale a long-range order is induced by the MgO interface, explaining the high tunnel magnetoresistance values > 100% even for not fully crystallized CoFeB/MgO/CoFeB tunnel junctions. (C) 2009 American Institute of Physics. [DOI:10.1063/1.3100044
Giant nonlocal damping by spin-wave emission: Micromagnetic simulations
No full textA micromagnetic simulation scheme is employed to evaluate the damping processes occurring in all-optical pump-probe experiments. We reveal that small wavelength and high-energy, nanometer-sized domains form during the first stage of the relaxation process. The emission of spin waves propagating out of the excitation spot area dominates the energy dissipation process. This process becomes dominant for small excitation spot areas and increases the macroscopically observed damping constant alpha drastically. We find that the damping time can be increased by a factor of more than 100, depending on the geometry, and must be considered in the interpretation of all-optical pump probe experiments with spot diameters less than 1 mu m
Spin-wave population in nickel after femtosecond laser pulse excitation
No full textThe spin-wave relaxation mechanisms after intense laser excitation in ferromagnetic nickel films are investigated with all-optical pump-probe experiments. Uniform precession (Kittel mode), Damon-Eshbach surface modes and perpendicular standing spin waves can be identified by their dispersion omega(H-ext). However, different to other ferromagnets omega(H-ext) deviates from the expected behavior. Namely, a mode discontinuity is observed that can be attributed to a nonlinear process. Above a critical field the power spectrum reveals a redistribution of the energy within the spin-wave spectrum populated.Academy of Sciences of the Czech Republic [KAN400100653
Intrinsic and nonlocal Gilbert damping parameter in all optical pump-probe experiments
No full textThe study of magnetization dynamics on the femtosecond time scale is an important task for the implementation of future ultrafast spintronics. With the time resolution inherent using femtosecond laser pulses in all optical pump-probe experiments, the basic time constants of magnetic precessional modes as well as the energy dissipation processes, which determine the Gilbert damping, can be studied. The dominant magnetic relaxation modes for the thin Ni films have frequencies in the range of 1.5-13 GHz. The corresponding Gilbert damping parameter is found to be dependent on the precession mode. The alpha values range from 0.05 to 0.8 for highly damped modes. The nonlocal Gilbert damping due to evanescent spin currents and two-magnon scattering is studied for double layers Ni/Cr/Si(100) with varied Ni thicknesses. A large increase of the damping parameter for films with a thinner Ni layer is observed. (C) 2006 American Institute of Physics
Disturbance of tunneling coherence by oxygen vacancy in epitaxial Fe/MgO/Fe magnetic tunnel junctions
No full textOxygen vacancies in the MgO barriers of epitaxial Fe/MgO/Fe magnetic tunnel junctions are observed to introduce symmetry-breaking scatterings and hence open up channels for noncoherent tunneling processes that follow the normal WKB approximation. The evanescent waves inside the MgO barrier thus experience two-step tunneling, the coherent followed by the noncoherent process, and lead to lower tunnel magnetoresistance, higher junction resistance, as well as increased bias and temperature dependence. The characteristic length of the symmetry scattering process is determined to be about 1.6 nm
Course System Architecting for Management
No full textThis article describes the condensed version the course System Architecture by the Center for Technical Training CTT. Trainer is the author of this article Gerrit Muller. At this moment this course is only accessible for Philips Employees
Magnetization dynamics in optically excited nanostructured nickel films
No full textIn this work, the laser-induced magnetization dynamics of nanostructured nickel films is investigated. The influence of the nanosize is discussed considering the timescale of hundreds of femtoseconds as well as the GHz regime. While no nanosize effect is observed on the short timescale, the excited magnetic mode in the GHz regime can be identified by comparison with micromagnetic simulations. The thickness dependence reveals insight into the dipole interaction between single nickel structures. Also, transient reflectivity changes are discussed.Deutsche Forschungsgemeinschaf
Elastic and inelastic conductance in Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions
No full textA systematic analysis of the bias voltage and temperature dependence of the tunneling magnetoresistance (TMR) in Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions with barrier thickness t(B) between 1.8 and 4.0 nm has been performed. The resistance measured at low temperature in the parallel state shows the expected exponential increase with increasing barrier thickness. The low-temperature TMR amplitude of about 300% is quite similar for all MgO thicknesses. This is in accordance with microstructural investigations by transmission electron microscopy, which do not give hints to a reduction in the barrier quality with increasing MgO thickness. Both the junction resistance and TMR decrease with increasing temperature and bias voltage. In general, the decrease is much stronger for thicker barriers, e. g., a decrease in the TMR by a factor of 13.4 from 293% at 15 K to 21.9% at 300 K was observed for t(B) = 4.0 nm compared to a reduction by only a factor of 1.6 for t(B) = 1.8 nm. This behavior can be described self-consistently for all barrier thicknesses within a model that extends the magnon-assisted tunneling model by adding an inelastic, unpolarized tunneling contribution. Furthermore we discuss our results in the framework of a recent model by Lu et al. [Phys. Rev. Lett. 102, 176801 (2009)] claiming that polarized hopping conductance becomes important for larger MgO thickness
An extraordinary photograph: Gerrit Rietveld, Mart Stam and El Lissitzky at the Schröder House, 1926
No full textThe Schröder House, designed in 1924 by Gerrit Th. Rietveld (1888-1964) in closecollaboration with the client Truus Schröder-Schräder (1889-1985), has beenphotographed countless times.1 Most of the photographs of this well-knownmonument are architectural photographs, of its exterior or interior. Only a fewof them include one or both of the designers. One such photograph, from 1926,appears in many publications concerning Rietveld or the Schröder House. It is anintriguing shot; but what exactly does it tell us?Heritage & Value
Gerrit Rietveld 's shop designs in the Netherlands from 1922 to 1962
No full textThis essay investigates the shops as well as commercial buildings designed by Gerrit Rietveld in the Netherlands from 1922 to 1962, focusing on the relation between the interior and the exterior in each project. Gaining insight into his contribution to the history of shop designs. This research has been conducted through a combination of literature study, and the archive of Gerrit Rietveld in the Het Nieuwe Instituut in Rotterdam, and provides elaboration on themes as the designs of the shop front, the interior, and the connection between them. These themes are addressed through observation of the images, and drawings in the archive and other resources. The essay also provides a critical view for the role of those shops in history, and their influences on subsequent shop designs after that. AR2A011Architecture, Urbanism and Building Science
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