Search results for " matter"
showing 10 items of 15893 documents
Superconductivity near a magnetic domain wall
2018
We study the equilibrium properties of a ferromagnetic insulator/superconductor structure near a magnetic domain wall. We show how the domain wall size is affected by the superconductivity in such structures. Moreover, we calculate several physical quantities altered due to the magnetic domain wall, such as the spin current density and local density of states, as well as the resulting tunneling conductance into a structure with a magnetic domain wall.
Non-Markovian Dynamics of a Qubit Due to Single-Photon Scattering in a Waveguide
2018
We investigate the open dynamics of a qubit due to scattering of a single photon in an infinite or semi-infinite waveguide. Through an exact solution of the time-dependent multi-photon scattering problem, we find the qubit's dynamical map. Tools of open quantum systems theory allow us then to discuss the general features of this map, find the corresponding non-Linbladian master equation, and assess in a rigorous way its non-Markovian nature. The qubit dynamics has distinctive features that, in particular, do not occur in emission processes. Two fundamental sources of non-Markovianity are present: the finite width of the photon wavepacket and the time delay for propagation between the qubit …
Coexistence of superconductivity and spin-splitting fields in superconductor/ferromagnetic insulator bilayers of arbitrary thickness
2021
Ferromagnetic insulators (FI) can induce a strong exchange field in an adjacent superconductor (S) via the magnetic proximity effect. This manifests as spin splitting of the BCS density of states of the superconductor, an important ingredient for numerous superconducting spintronics applications and the realization of Majorana fermions. A crucial parameter that determines the magnitude of the induced spin splitting in FI/S bilayers is the thickness of the S layer d: In very thin samples, the superconductivity is suppressed by the strong magnetism. By contrast, in very thick samples, the spin splitting is absent at distances away from the interface. In this work, we calculate the density of …
High-pressure characterization of multifunctional CrVO4
2020
[EN] The structural stability and physical properties of CrVO(4)under compression were studied by x-ray diffraction, Raman spectroscopy, optical absorption, resistivity measurements, andab initiocalculations up to 10 GPa. High-pressure x-ray diffraction and Raman measurements show that CrVO(4)undergoes a phase transition from the ambient pressure orthorhombic CrVO4-type structure (Cmcm space group, phase III) to the high-pressure monoclinic CrVO4-V phase, which is proposed to be isomorphic to the wolframite structure. Such a phase transition (CrVO4-type -> wolframite), driven by pressure, also was previously observed in indium vanadate. The crystal structure of both phases and the pressure …
Spin filtering by proximity effects at hybridized interfaces in spin-valves with 2D graphene barriers
2020
We report on spin transport in state-of-the-art epitaxial monolayer graphene based 2D-magnetic tunnel junctions (2D-MTJs). In our measurements, supported by ab-initio calculations, the strength of interaction between ferromagnetic electrodes and graphene monolayers is shown to fundamentally control the resulting spin signal. In particular, by switching the graphene/ferromagnet interaction, spin transport reveals magneto-resistance signal MR > 80% in junctions with low resistance × area products. Descriptions based only on a simple K-point filtering picture (i.e. MR increase with the number of layers) are not sufficient to predict the behavior of our devices. We emphasize that hybridization …
Angular dependence of the domain wall depinning field in the sensors with segmented corners
2017
Rotating domain wall based sensors that have recently been developed are based on a segmented looping geometry. In order to determine the crucial pinning of domain walls in this special geometry, we investigate the depinning under different angles of an applied magnetic field and obtain the angular dependence of the depinning field of the domain walls. Due to the geometry, the depinning field not only exhibits a 180$^\circ$-periodicity but a more complex dependence on the angle. The depinning field depends on two different angles associated with the initial state and the segmented geometry of the corner. We find that depending on the angle of the applied field two different switching proces…
Controlled turbulence regime of electron cyclotron resonance ion source for improved multicharged ion performance
2020
Fundamental studies of excitation and non-linear evolution of kinetic instabilities of strongly nonequlibrium hot plasmas confined in open magnetic traps suggest new opportunities for fine-tuning of conventional electron cyclotron resonance (ECR) ion sources. These devices are widely used for the production of particle beams of high charge state ions. Operating the ion source in controlled turbulence regime allows increasing the absorbed power density and therefore the volumetric plasma energy content in the dense part of the discharge surrounded by the ECR surface, which leads to enhanced beam currents of high charge state ions. We report experiments at the ECR ion source at the JYFL accel…
Effect of space charge on the negative oxygen flux during reactive sputtering
2017
Negative ions often play a distinctive role in the phase formation during reactive sputter deposition. The path of these high energetic ions is often assumed to be straight. In this paper, it is shown that in the context of reactive magnetron sputtering space charge effects are decisive for the energetic negative ion trajectories. To investigate the effect of space charge spreading, reactive magnetron sputter experiments were performed in compound mode with target materials that are expected to have a high secondary ion emission yield (MgO and CeO2). By the combination of energy flux measurements, and simulations, a quantitative value for the negative oxygen ion yield can be derived.
Determination of an empirical law of aluminium and magnesium alloys absorption coefficient during Nd :YAG laser interaction
2007
International audience; Welding laser modelling requires knowledge about relative changes of many thermo-physical parameters involved in the interaction. The absorptivity of the material is one of the most important. In this study, experimental measurements of absorptivity with an integrating sphere on two alloys (aluminium and magnesium) were made. These results were compared with an analytical calculation that takes into account the trapping of the beam by multiple reflections inside the keyhole. Based on a statistical method, an empirical law is proposed connecting absorptivity with the peak power of the laser and the duration of interaction. During the interaction, two distinct phenomen…
Evolution of the microstructure of sputter deposited TaAlON thin films with increasing oxygen partial pressure
2021
Abstract Recently, quaternary oxynitrides of transition metals and aluminum have attracted increasing interest due to their tunable properties. Within the present work, a series of TaAl(O)N films was sputter deposited using constant nitrogen and varying oxygen partial pressures. The films were grown from single element Ta and Al targets. The deposition parameters were adjusted to obtain a Ta/Al atomic ratio of ~50/50 for the oxygen-free film and were held constant for the following depositions, with the exception of the increasing oxygen partial pressure and compensatory decreasing argon partial pressure. Elastic recoil detection analysis revealed oxygen contents of up to ~26 at.%, while th…