M. von Ortenberg

Magnetization of ZnFeSe semimagnetic semiconductors

Abstract Magnetization of Zn 1− x Fe x Se ( x ⩽ 0.13) was measured for the temperature range 2–50 K in magnetic fields of up to 15 T. Temperature independent paramagnetism was observed between 2 and 6 K and is interpreted on the basis of Van Vleck-type paramagnetism.

Substrate effects on the cyclotron resonance in surface layers of silicon

Abstract A detailed analysis is applied to surface-cyclotron resonance experiments using plane-parallel silicon substrates and demonstrates the substantial influence of optical interference effects on position and shape of the cyclotron-resonance line in transmission spectra.

Structural properties of perfect ZnTe epilayers on (001) GaAs substrates

Abstract We report on molecular beam epitaxy and hot-wall beam epitaxy growth of ZbTe epilayers on (001) GaAs substrates. The surface reconstruction of (001) ZnTe is measured by reflection high-energy electron diffraction (RHEED). The RHEED pattern as a function of the beam equivalent pressure ratio p Te / P Zn and substrate temperature is studied. Mosaic structures of the ZnTe epilayers grown under optimized conditions are investigated quantitatively by high resolution X-ray diffraction and photoluminescence. These data, which are related to the three-dimensional perfection of epilayers, are contrasted to RHEED measurements of the surface morphology.

ARMS: A Successful European Program for an 80 T User Magnet

ARMS is the acronym for Advanced Research Magnet Systems, a project under the European Unions 5th Framework Research Infrastructures program (HPRI-CT-1999-50007). Eight partners throughout Europe cooperated in ARMS, which was coordinated by the University of Oxford, UK. The objective of the project was to build an 80 T user magnet to be installed at LNCMP, Toulouse, France. The approach chosen was the coil-ex/coil-in method, whereby a large outer coil was energized by LNCMPs unique, 14 MJ capacitor bank. The inner coil was energized by a fast, 100 kJ bank at the peak of the outer coils field. In this paper the evolution of the coils, the conductors and other materials is outlined as is the testing and ultimate, successful use in physics experiments up to 76 T. A view of the future direction of high pulsed fields in Europe, post-ARMS, will also be given

High-field magneto-spectroscopy on p-type GaAs/GaAlAs heterojunctions

Abstract Experimental multi-line spectra of submillimeter-laser magneto-spectroscopy on p-type GaAs/GaAlAs heterojunctions in magnetic fields up to 30 T are presented and discussed in context with recent theoretical results. For magnetic fields B > 20 T, transitions are observed, which are not predicted by the Landau-level calculations.

The Megagauss facility of the HUMBOLDT high magnetic field center in Berlin

Abstract We report on concept. realisation, and first experimental results obtained with the preliminary megagauss equipment of the HUMBOLDT High Magnetic Field Center. The present megagauss set-up is a handy, transportable single-turn coil equipment using only 20% of the capacity of the final installation, i.e. 50 kJ at 60 kV producing about 100 and 200 T in the single-turn coils of 10 and 5 mm diameter, respectively. Test reports on magnetooptical measurements at low temperature are presented.

Fir spectroscopy of Fe-based semimagnetic semiconductors

We report far-infrared studies of low energy levels of Fe2+ ions in ZnSe and related wide-gap semimagnetic semiconductors in magnetic fields up to 20 T. Transitions between 5E levels are observed and the experimental results are in good agreement with the standard model of single iron impurities in a AIIBVI host lattice. No significant contribution of iron pairs is observed, at least for Fe concentrations up to a few percent. The influence of Jahn-Teller effects will be shortly discussed.

Magnetic freeze-out in indiumantimonide

Abstract The reduction of the free electron concentration is pure n-type InSb as a function of a strong magnetic field was calculated for different temperatures and various degrees of compensation. The non-parabolicity, the g-factor and the excited impurity states were taken into account.

FIR absorption of Zn1−xCrxS

Abstract The energy level structure of Cr2+ in polytypical ZnCrS in applied magnetic fields was studied using far infrared laser and millimeter wave absorption in the energy range 1.4–25 cm−1. The magnetic fields up to 20 T were oriented along the (1 1 1) or (1 1 0) crystal axis. A strong anisotropy of absorption lines is observed. The description of the data is provided by a cubic crystal field model with a static Jahn-Teller distortion included.

Far-infrared magneto-absorption of donor-bound excitons in germanium: Pseudo-acceptor model

Abstract The magneto-oscillatory absorption spectrum of the arsenic-bound excitons in germanium observed at 118.6 μm reveals a series of absorption lines similar to the Zeeman spectrum of the acceptor impurity. This fact indicates that the bound excitons have the excited states associated with the light-hole Landau ladders and these excited states can be described by the model of a hole bound to the D- state, i.e. the pseudo-acceptor model. The hole binding energy of the ground state of the bound excitons has been obtained to be 4.7 meV, which is smaller compared with the binding energy of the acceptor impurity.