Researches in spintronics, especially those remarkably classified in the current induced spin-transfer torque (STT) framework, circumvent challenges with different materials and geometries. Perpendicular magnetic anisotropy (PMA) materials are showing capability of holding promise to be employed in STT based spintronics elements, e.g. spin-torque oscillators (STOs), STT-magnetoresistive random access memories (STT-MRAMs) and current induced domain wall motion elements. This dissertation presents experimental investigations into developing sputter deposited Co/Ni multilayers (MLs) with PMA and employs these materials in nano-contact STOs (NC-STOs) based on giant magnetoresistance (GMR) effect and in pseudo-spin-valve (PSV) structures. The magnetostatic stray field coupling plays an important role in perpendicular PSVs. The temperature dependent coupling mechanism recommends that this coupling can be tailored, by i) the saturation magnetization and coercivity of the individual layers, ii) the coercivity difference in layers, and iii) the GMR spacer thickness, to get a well decoupled and distinguishable switching response. Moreover, this thesis focused on the implementation and detailed characterization of NC-STOs with strong PMA Co/Ni ML free layers and in-plane Co reference layers as orthogonal (Ortho) magnetic geometry in so-called Ortho-NC-STOs. The primary target of reaching record high STO frequencies, 12 GHz, at close to zero field, 0.02 Tesla, was achieved. However, in large external fields, &gt;0.4 Tesla, an entirely new magnetodynamic object, a “magnetic droplet”, theoretically predicted in 1977, was discovered experimentally. Detailed experiments, combined with micromagnetic simulations, demonstrate the formation of a magnetic droplet with a partially reversed magnetization direction underneath the NC, and a zone of large amplitude precession in a region bounding the reversed magnetization. The magnetic droplet exhibits a very rich dynamics, including i) auto-modulation as a combine of droplet frequency with a slow time evolution (few GHz) of un-centering the droplet mode under the NC, ii) droplet breathing as reversible deformation of droplet mode with ½ droplet frequency. All observation of droplet opens a new mechanism of excitation for future fundamental studies as well as experiments especially for domain wall electronics and nano-scopic magnetism. / <p>QC 20121119</p>

Areal densities of perpendicular hard-disk drives over 500Gb/in2 have already been demonstrated, with 1Tb/in2 densities being forecasted in the near future. However, at these high areal densities the information bearing units on the magnetic storage medium are magnetically unstable at temperatures expected in hard-disk drives. To extend or bypass this limit, new developments in head and media technologies and understanding of their record, readout and noise performances are necessary. The aim of this project was to study the record, readout and noise properties of conventional and future perpendicular magnetic recording media, heads and their related technologies. The objectives were therefore to develop a flexible and robust experimental recording platform to test the performance of different heads and media, and develop the necessary readout theory to predict the replay performance. In line with the project objectives, a high-precision open contact recording tester was developed with 1nm resolution. The open nature of this system allows different heads and media combinations to be tested. A second, closed system was also developed based on a commercial perpendicular hard-drive, modified to serve as a spin-stand to provide signal and noise measurements in practical drive conditions. The readout process in perpendicular recording was modelled based on the reciprocity principle for a shielded TMR head to study the parameters that affect the readout signal performance, and for comparison with the experimental measurements. Measured signal roll-off curves showed a practical linear density of 450KFCI for the commercial perpendicular disk medium, and indicated that non-linear effects happen at linear densities approaching 550KFCI. These results were in agreement with the theoretical calculations of the replay process. Two-dimensional readout scans were found have similar or higher resolution than Magnetic Force Microscopy (MFM) images of the same recorded regions – indicating the versatility and precision of the developed contact tester. Inverse filtering employing the Wiener filter was used to extract the magnetic transition. The extracted transition profiles and transition extents from the replay signals had much higher resolution than MFM images measured for the same transition region, thus showing the applicability of the developed testers for in situ magnetic characterisation. The developed contact and non-contact testers allowed the investigation of a new proposed recording scheme, Shingled Magnetic Recording (SMR). Measured signal roll-off curves of shingled tracks indicated a rise in the signal amplitude at low densities. At higher linear densities the signal performance was the same as conventionally written tracks with guardbands. It was found that a 30% reduction in track width in SMR, increase the areal density by a factor of 1.58 above that in existing hard drives.

In this thesis the author describes the use of transient grating techniques to study the transport of electrons and holes perpendicular to the layers of a GaAs/AlGaAs multiple quantum well (MQW).

The accurate prediction of warm-season convective systems, and the heavy rainfall and severe weather associated with them, remains a challenge for numerical weather prediction models. This study looks at one such circumstance in which back-building convection forms perpendicular to, and above the cold pool region behind strong bow echoes. We refer to this phenomenon as a "bow and arrow" because, on radar imagery, the two convective lines resemble an archer's bow and arrow. The "arrow" can extend over hundreds of kilometers and can cause damage from high winds, hail and flooding. Events of this nature pose a particular challenge to forecast because they require an accurate forecast of the earlier convection and the effects of that convection on the environment. In this study, radar and surface observations of four events are presented to identify common environmental conditions prior to the development of the back-building convection. Additionally, simulations of three cases using the Weather Research and Forecasting (WRF) model are analyzed in an attempt to understand the mechanisms responsible for initiating and maintaining the convective line. Due to coarse resolution, observational analyses are only useful for inspection of the synoptic-scale. Model output from numerical simulations is utilized to examine the mesoscale in the vicinity of the convective arrow. Several environmental characteristics are evident in each of the studied cases. Strong southwesterly flow (inducing warm air advection and gradual isentropic lifting), in addition to directional and speed convergence into the convective arrow region possibly contribute to convection initiation. Horizontal wind speed shear and increased wind speed in the area surrounding the arrow may be associated with the linear orientation of the arrow. It seems as though when these ingredients are combined with thermodynamic instability, there is a greater possibility of formation and maintenance of a convective arrow behind a bow echo.

El presente trabajo de título tiene como objetivo encontrar un óptimo teórico para la potencia entregada por una forma de onda en la banda de frecuencia donde la sensibilidad táctil es máxima 25-700Hz. Además se realiza un estudio experimental para establecer si existen diferencias significativas entre dos tipos de estimulación mecánica a la piel: tangencial y perpendicular

A componente perpendicular à costa das correntes nas plataformas continentais é comumente menos intensa e energética do que a componente paralela. Entretanto, elas são importantes no contexto da circulação normal à costa e da troca de água entre plataformas continentais e oceano aberto. Este trabalho teve por finalidade compreender o comportamento das correntes perpendiculares à costa na parte setentrional da Plataforma Continental Sudeste Brasileira (PCSE). Para tal, utilizou-se quatro anos de dados de correntometria do projeto DEPROAS em fundeios de 50, 100 e 200 metros de profundidades nas radiais de Cabo Frio, Ubatuba e Baia de Guanabara para diversas análises e procedimentos estatísticos, assim como experimentos numéricos utilizando-se o modelo computacional sECOM. Esses dados foram comparados com parâmetros adimensionais (número de Burger) afim de descrever os principais padrões de resposta dessas correntes às diversas condições nos espectros temporais e espaciais. O número de Burger (S) é um bom parâmetro para descrever o a dinâmica perpendicular na PCSE. Regiões com S próximo ou maior do que um (principalmente próximas ao talude) transportam água, para a plataforma principalmente acima da camada de fundo, devido ao rápido desligamento da camada de Ekman (períodos menores do que os subinerciais). Consequentemente, nas regiões dos fundeios das isóbatas de 200 metros, registrou-se a exportação de água da plataforma para o oceano aberto próximo ao fundo associados à maré diurna. / The cross-shore current on continental shelves are usually less intense and energetic than the alongshore current. However, they are important in characterizing the cross shelf circulation and the exchange of water between the continental shelf and the open ocean. This paper aims to understand the behavior of cross-shore currents on the northern part of the Southeast Brazilian Continental Shelf. It was used four years of current data from DEPROAS project\'s moorings (50, 100 and 200 meters depths) from cross-sections in Cabo Frio, Ubatuba and Guanabara Bay. Those data were statistically treated and analyzed. In addition, it was conducted numerical experiments with sECOM computational model. Those data were compared with dimensionless parameters (Burger number) in order to describe the main response patterns of them during different temporal and spatial conditions. The Burger number (S) is a good parameter to describe the cross-shelf dynamics in the studied area. When S is near or greater than one (especially near the slope) the water fluxes directed to the platform occurs mainly above the bottom layer due to the rapid shutdown of Ekman layer. Consequently, nearby the 200 meters isobaths, the water is exported to the open ocean near seabed associated with diurnal tide.

Spintronics discusses about fundamental physics and material science in mostly nanometer size structures. Spintronics also delivers many promising technologies for now and the future. One of the interesting spintronic structures is called “Magnetic Tunnel junction” (MTJ). A typical MTJ consists of a thin (1-3nm) insulator layer sandwiched between two ferromagnetic layers. In this work, I present MTJ with perpendicular magnetic anisotropy (PMA) using an MgO tunnel barrier. The effect of different heavy metals (HMs) adjacent to the ferromagnets (FMs) on tunneling magnetoresistance (TMR) and PMA of the junctions are discussed. Namely, Ta, Mo, Ta/Mo, W, Ir, and Hf have been utilized in HM/FM/MgO structures, and magneto-transport properties are explored. It is shown that when Ta/Mo is employed, TMR values as high as 208%, and highly thermally stable PMA can be obtained. Some physical explanation based on electronic band structure and thermochemical effects are discussed. In the last part of this work, the newly discovered tunneling anisotropic magnetoresistance (TAMR) effect in antiferromagnets is studied, and clear TAMR is demonstrated for NiFe/IrMn/MgO/Ta structures.

A componente perpendicular à costa das correntes nas plataformas continentais é comumente menos intensa e energética do que a componente paralela. Entretanto, elas são importantes no contexto da circulação normal à costa e da troca de água entre plataformas continentais e oceano aberto. Este trabalho teve por finalidade compreender o comportamento das correntes perpendiculares à costa na parte setentrional da Plataforma Continental Sudeste Brasileira (PCSE). Para tal, utilizou-se quatro anos de dados de correntometria do projeto DEPROAS em fundeios de 50, 100 e 200 metros de profundidades nas radiais de Cabo Frio, Ubatuba e Baia de Guanabara para diversas análises e procedimentos estatísticos, assim como experimentos numéricos utilizando-se o modelo computacional sECOM. Esses dados foram comparados com parâmetros adimensionais (número de Burger) afim de descrever os principais padrões de resposta dessas correntes às diversas condições nos espectros temporais e espaciais. O número de Burger (S) é um bom parâmetro para descrever o a dinâmica perpendicular na PCSE. Regiões com S próximo ou maior do que um (principalmente próximas ao talude) transportam água, para a plataforma principalmente acima da camada de fundo, devido ao rápido desligamento da camada de Ekman (períodos menores do que os subinerciais). Consequentemente, nas regiões dos fundeios das isóbatas de 200 metros, registrou-se a exportação de água da plataforma para o oceano aberto próximo ao fundo associados à maré diurna. / The cross-shore current on continental shelves are usually less intense and energetic than the alongshore current. However, they are important in characterizing the cross shelf circulation and the exchange of water between the continental shelf and the open ocean. This paper aims to understand the behavior of cross-shore currents on the northern part of the Southeast Brazilian Continental Shelf. It was used four years of current data from DEPROAS project\'s moorings (50, 100 and 200 meters depths) from cross-sections in Cabo Frio, Ubatuba and Guanabara Bay. Those data were statistically treated and analyzed. In addition, it was conducted numerical experiments with sECOM computational model. Those data were compared with dimensionless parameters (Burger number) in order to describe the main response patterns of them during different temporal and spatial conditions. The Burger number (S) is a good parameter to describe the cross-shelf dynamics in the studied area. When S is near or greater than one (especially near the slope) the water fluxes directed to the platform occurs mainly above the bottom layer due to the rapid shutdown of Ekman layer. Consequently, nearby the 200 meters isobaths, the water is exported to the open ocean near seabed associated with diurnal tide.

The goal of this master’s thesis is design of belt bucket elevator for wheat transportation. The first part of this thesis is focused on drive’s design with slightly marked bond to surrounding facilitie and structure. The following part is focused on design solution of the head and bottom unit of bucket elevator and other constructive details like type of bucket pouring, belt tensioning, driving shaft mounting in head unit, connection of drum with shaft, the way of attaching buckets etc.

No description available.