Heterostructures with InGaAs/GaAs quantum dots doped with transition elements: II. Study of the circularly polarized luminescence

Optical and transport properties of the heterostructure with the InAs/GaAs quantum dots doped with manganese or chromium atoms in the course of growth using metal-organic vapor phase epitaxy (MOVPE) are analyzed. Circularly polarized luminescence was obtained due to doping of quantum dots with the Mn or Cr atoms. The sign of the degree of circular polarization was found to depend on the dopant. The effect is interpreted using specific features of the radiative recombination in quantum dots in the presence of resident electrons and holes.     

A (Ga,Mn)Sb magnetic semiconductor for spintronic applications

The structural, optical, and galvanomagnetic properties of (Ga, Mn)Sb layers grown by the laser sputtering of solid targets in H₂ flow are n studied. It is shown that at a growth temperature of 400°C, (Ga, Mn)Sb layers are single-crystal up to high Mn concentrations. The magnetic field dependence of the Hall resistance at measuring temperatures of 10–300 K contains a hysteresis loop; i. e., the layers are ferromagnetic semiconductors.     

Methods for spin injection managing in inGaAs/GaAs/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/CoPt spin light-emitting diodes

Spin injection in CoPt/Al₂O₃/(Al)GaAs spin light-emitting diodes (SLEDs) was studied. The oscillations of the degree of circular polarization upon variation of a distance between the active region of the SLED and a CoPt ferromagnetic injector were observed. The oscillations depend neither on a SLED material (GaAs or AlGaAs), nor on the type of injected spin-polarized carriers (electrons and holes) and are related to the action of a perpendicular magnetic field on the injected spin-polarized carriers that causes their precession. During the transfer to the active region through a distance of 50–100 nm from the injector, a z–component of a spin changes a phase that is detected experimentally as the change in sign of the degree of circular polarization of luminescence. Conceivably, a source of the internal magnetic field leading to spin precession is the magnetic field of the nonuniformly magnetized CoPt contact.     

Wave emission from a VLF plasma-waveguide antenna system under ionospheric conditions

We study a VLF plasma-waveguide antenna system having the form of a field-aligned quasicylindrical enchancement of plasma density, which relaxes gradually to the background magnetoplasma with distance from the given source. A model enabling one to calculate both the total radiated power and the power distribution over the spatial spectrum of radiated waves is proposed. It is shown that this plasma antenna is useful for increasing the power going to the long-wave part of the spatial spectrum of whistler waves excited in the ambient plasma. Concrete estimates for terrestrial ionospheric conditions are given.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 2, pp. 210–225, February, 1996.The work of the first two authors was supported in part by the Russian Foundation for Fundamental Research (Project codes No. 95-02-05001 and No. 94-02-05447-a, respectively). The work of the third author (A. V. Kudrin) was supported by the Russian Foundation for Fundamental Research under Grant No. 96-02-18666.     

Radiation of whistler waves in a magnetized plasma medium in the presence of density ducts

We investigate the influence of density ducts on the radiation of given sources in a magnetoplasma. We obtain the full-wave solution for the problem of radiation from annular electric and magnetic currents in the presence of a plasma column (density duct) oriented along an external magnetic field and surrounded by a uniform background magnetoplasma. Both the discrete part of the spatial spectrum of excited waves and the continuous part of the spectrum are considered. We calculate the total radiated power and partial powers radiated in separate eigenmodes guided by the column. It is established that in the whistler frequency range the presence of a channel with enhanced plasma density can cause a considerable increase in the radiation power of annular sources. We give concrete estimations for the ionospheric conditions and compare these results with the results obtained previously for the case of a uniform magnetoplasma without density ducts.Nizhnii Novgorod University. Tranlated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 7, pp. 887–908, July, 1994.     

Phase Separation in GaMnAs Layers Grown by Laser Pulsed Deposition

GaMnAs layers grown by pulsed laser deposition were studied by magneto-optical transversal Kerr effect spectroscopy, spectral ellipsometry, resistivity and the Hall effect measurements, and magnetometry. The growth regimes for magnetically inhomogeneous layers containing Mn-enriched ferromagnetic regions with different composition and sizes were established. The layers grown at a temperature of 300°C exhibit a ferromagnetic behavior at temperatures below 80 K, which is conditioned by the presence of local ferromagnetic (Ga,Mn)As regions in the paramagnetic matrix. The nature of peculiarities in the TKE spectrum of these layers is discussed.     

Radiation of Whistler Waves from a Source with a Rotating Near-Zone Magnetic Field in a Magnetoplasma

Radiophysics and Quantum Electronics - We study radiation from given nonsymmetric currents which are located in a homogeneous cold magnetoplasma and produce a rotating near-zone magnetic field....     

Theory of a Strip Antenna Located at a Plane Interface of a Uniaxial Magnetic Metamaterial and an Isotropic Medium

Technical Physics - Electrodynamic characteristics of an antenna in the form of an infinitesimally thin, perfectly conducting narrow strip located at a plane interface of a uniaxial magnetic...     

Development of a Standard for Verification of the System for Automated Morphometry of Clinical Images of Skin Neoplasms

Optics and Spectroscopy - Technological and metrological specifics were considered for developing a standard for calibration and verification of a system that performs automated morphometry of skin...     

Whistler Wave Emission from a Modulated Electron Beam in a Collisional Magnetoplasma in the Presence of a Density Duct

We study the radiation from a modulated electron beam injected along the axis of a cylindrical density duct in a magnetoplasma. An expression for the average power lost by the beam at the modulation frequency is obtained and analyzed. It is shown that in the case of Cerenkov resonance of the beam with a weakly damped whistler mode of an enhanced-density duct, a noticeable increase in this power is possible compared with the case where the beam is injected in a homogeneous background magnetoplasma. Based on the results of numerical calculations performed for conditions of the Earth's ionosphere, we give estimates of an increase in the power radiated from the beam in the whistler frequency range in the presence of a cylindrical duct with enhanced density. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 9, pp. 730–742, September 2005.