Self-Consistent Calculations of Landau Levels for Symmetric p-Type Inversion Layers

A method for calculating the Landau levels of symmetric p-type inversion layers is presented. Using the envelope function approach in the Hartree approximation the magnetic field is incorporated into the Hamiltonian. In order to characterize the energy levels and to obtain a detailed understanding of the unusual Landau scheme, an analysis of the wave functions is made. Special effects are discussed for the inversion layers adjacent to the grain boundary of a Ge-bicrystal, with two occupied subbands. The simulation of Shubnikov-de Haas data by a density of states analysis shows that the different oscillatory periods are not directly related to the subband occupations.     

A comparative study of the electric giant dipole resonance of 24−26Mg

The electric giant dipole resonance of ^24?26Mg has been explored up to 30 MeV excitation energy with bremsstrahlung. ΔE, E spectra of charged photo-particles and spectra of prompt deexcitation γ-rays from excited residual nuclear states were obtained at various bremsstrahlung endpoint energies. The ²⁵Mg(γ, p₀), (γ, d), ^24,25Mg(γ, α) differential cross sections as well as ^24?26Mg(γ, xγ′) integrated cross sections are presented. The results are discussed in terms of one-particle, one-hole excitations and isospin composition of giant resonance states. A comparison with calculations for ²⁴Mg gives poor agreement. Excitations from deeper shells were found in the giant dipole resonance of ²⁴Mg, but do not seem to be concentrated at higher energies. In ²⁵Mg, only weak excitations of this kind were found, and they are completely absent in ²⁶Mg.     

Stability of magnetic tunnel junctions

When magnetic tunnel junctions (MTJ) are built into a memory device they will be arranged in a matrix; therefore some of the not addressed elements will be exposed to a significant field during the switching of one element. It has to be avoided that the state of not selected MTJ is changed during this process. Here we present data on the stability of MTJ against small fields which occur during a writing process.     

Ultramicrohardness tester for use in a scanning electron microscope

Summary A novel microhardness-tester has been designed for loads between 10^–2 N and 5 x 10^–5 N. The apparatus can be operated in a scanning electron microscope without installation of additional adjusting shafts. The force is generated electromagnetically, transduced to the indenter (diamond cone or pyramid) by bending a double leaf spring, and measured by means of strain gauges fixed to the springs. The indentation cycle is fully programmable and is controlled by the strain gauge signal. The equipment can be tilted with respect to the electron beam thus making possible the observation of the tip during indentation.With 2 figures     

Trapping quasiminimizing submanifolds in spaces of negative curvature

LetM be a Hadamard manifold with all sectional curvatures bounded above by some negative constant. A well-known lemma essentially due to M. Morse states that every quasigeodesic segment inM lies within an a priori bounded distance from the geodesic arc connecting its endpoints. In this paper we establish an analogue of this fact for quasiminimizing surfaces in all dimensions and codimensions; the only additional requirement is that the sectional curvatures ofM be bounded from below as well. We apply this estimate to obtain new solutions to the asymptotic Plateau problem in various settings. The second author was supported by the Swiss National Science Foundation and enjoyed the hospitality of the University of Bonn. The collaboration between the authors was facilitated by the program GADGET II.