Search results for "HAL"
showing 10 items of 12326 documents
Impact of Annealing Temperature on Tunneling Magnetoresistance Multilayer Stacks
2020
The effect of annealing temperatures on the tunnel magnetoresistance (TMR) of MgO-based magnetic tunnel junctions (MTJs) has been investigated for annealing between 190 and 370°C. The TMR shows a maximum value of 215% at an annealing temperature of 330°C. A strong sensitivity of the TMR and the exchange bias of the pinned ferromagnetic layers on the annealing temperature are observed. Depending on sensor application requirements, the MTJ can be optimized either for stability and pinning strength or for a high TMR signal by choosing the appropriate annealing temperature. The switching mechanism of the ferromagnetic layers in the MTJ and the influence of the annealing on the layer properties,…
Arsenic diffusion in relaxedSi1−xGex
2003
The intrinsic As diffusion properties have been determined in relaxed ${\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{Ge}}_{x}$ epilayers. The properties were studied as a function of composition x for the full range of materials with $x=0,$ 0.20, 0.35, 0.50, 0.65, 0.8, and 1. The activation enthalpy ${E}_{a}$ was found to drop systematically from 3.8 eV $(x=0)$ to 2.4 eV $(x=1).$ Comparisons with other impurity atom- and self-diffusion results in Si, Ge, and SiGe show that both interstitials and vacancies contribute as diffusion vehicles in the composition range $0l~xl~0.35$ and that vacancy mechanism dominates diffusion in the composition range $0.35lxl~1.$
Spin–orbit torque driven multi-level switching in He + irradiated W–CoFeB–MgO Hall bars with perpendicular anisotropy
2020
We have investigated the spin–orbit torque-driven magnetization switching in W/CoFeB/MgO Hall bars with perpendicular magnetic anisotropy. He+ ion irradiation through a mask has been used to reduce locally the effective perpendicular anisotropy at a Hall cross. Anomalous Hall effect measurements combined with Kerr microscopy indicate that the switching process is dominated by domain wall (DW) nucleation in the irradiated region followed by rapid domain propagation at a current density as low as 0.8 MA/cm2 with an assisting in-plane magnetic field. Thanks to the implemented strong pinning of the DW at the transition between the irradiated and the non-irradiated region, an intermediate Hall r…
Efficiency of H center stabilization in alkali halide crystals at low-temperature uniaxial deformation
2020
The efficiency of stabilization of H centers as well as its dependence on the degree of uniaxial deformation are considered within the framework of the modified geometric model of alkali halides. It is shown that stabilization of H centers is difficult in KI and RbI crystals, while in other NaCl-type crystals it becomes quite probable. Under uniaxial deformation, the interstitial space, in which the defect will be located, decreases, and the efficiency decrease. In the case of cesium halides, the orientation of the H centers takes place predominantly in the direction; therefore, the criteria for their stabilization differ from the NaCl-type alkali halide crystals. According to calculations,…
The interdependence of structural and electrical properties in TiO2/TiO/Ti periodic multilayers
2013
International audience; Multilayered structures with 14-50 nm periods composed of titanium and two different titanium oxides, TiO and TiO2, were accurately produced by DC magnetron sputtering using the reactive gas pulsing process. The structure and composition of these periodic TiO2/TiO/Ti stacks were investigated by X-ray diffraction and transmission electronic microscopy techniques. Two crystalline phases, hexagonal close packed Ti and face centred cubic TiO, were identified in the metallic-rich sub-layers, whereas the oxygen-rich ones comprised a mixture of amorphous TiO2 and rutile phase. DC electrical resistivity rho measured for temperatures ranging from 300 to 500 K exhibited a meta…
Validation of a 3D mathematical model for feed rod melting during floating zone Si crystal growth
2019
Abstract A mathematical model of global 3D heat transfer in floating zone silicon single crystal growth process is used to predict the shape of the open melting front of the feed rod. The model is validated using measurement data from research-scale growth experiments. Shape profiles of the open melting front are obtained from the feed rod leftover using a movable dial gauge. Azimuthal asymmetry of the rim of the open melting front is revealed in both simulations and measurements, quantitatively indicating the influence of the main slit of the inductor.
Influence of surface topography on depth profiles obtained by Rutherford backscattering spectrometry
2000
A method for determining correct depth profiles from samples with rough surfaces is presented. The method combines Rutherford backscattering spectrometry with atomic force microscopy. The topographical information obtained by atomic force microscopy is used to calculate the effect of the surface roughness on the backscattering spectrum. As an example, annealed Au/ZnSe heterostructures are studied. Gold grains were observed on the surfaces of the annealed samples. The annealing also caused diffusion of gold into the ZnSe. Backscattering spectra of the samples were measured with a 2 MeV 4He+ ion beam. A scanning nuclear microprobe was used to verify the results by measuring backscattering fro…
High-frequency EPR study on Cu4Cu- and Co4Co-metallacrown complexes
2019
Abstract High-frequency/high-field electron paramagnetic resonance studies on two homonuclear 12-MC-4 metallacrown complexes Cu4Cu and Co4Co are presented. For Cu4Cu, our data imply axial-type g-anisotropy with g x = 2.03 ± 0.01 , g y = 2.04 ± 0.01 , and g z = 2.23 ± 0.01 , yielding g = 2.10 ± 0.02 . No significant zero field splitting (ZFS) of the ground state mode is observed. In Co4Co, we find a m S = ± 3 / 2 ground state with g = 2.66 . The data suggest large anisotropy D of negative sign.
Magnetic properties of exciton trapped by an off-center ionized donor in single quantum dot
2021
Abstract It is known that the lines of exciton (X) and exciton trapped by an ionized donor ( D + , X ) are often very close which makes very difficult their experimental identification. In order to facilitate their distinction in spherical quantum dots, we investigate the effect of an applied magnetic field studying the binding energy of the complex ( D + , X ) as function of dot size and the ionized donor position. Our calculation is using a variational approach taking into account the interactions between all charge carriers. Our results show that the complex is more sensitive to the magnetic field than the exciton and that the energy of the exciton is not sufficiently affected when the i…
Multiscale model approach for magnetization dynamics simulations
2016
Simulations of magnetization dynamics in a multiscale environment enable the rapid evaluation of the Landau-Lifshitz-Gilbert equation in a mesoscopic sample with nanoscopic accuracy in areas where such accuracy is required. We have developed a multiscale magnetization dynamics simulation approach that can be applied to large systems with spin structures that vary locally on small length scales. To implement this, the conventional micromagnetic simulation framework has been expanded to include a multiscale solving routine. The software selectively simulates different regions of a ferromagnetic sample according to the spin structures located within in order to employ a suitable discretization…