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All-semiconducting EuS/PbS/EuS trilayers that show antiferromagnetic coupling were studied by superconducting quantum interference device magnetometry. We analyzed our measurements with a modified Stoner–Wohlfarth model from which the interlayer exchange energy and anisotropy were extracted based on the switching field from antiparallel to parallel alignment of the EuS layers and the zero-field susceptibility, respectively. Magnetic moment versus temperature curves were simulated by taking into account Brillouin type temperature dependence of the saturation magnetization of EuS. Despite their simplicity, the simulated curves show good qualitative agreement with the measurements when strong temperature dependence of interlayer coupling is assumed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The results of investigation of structural and electrical properties of bulk SiC crystals, which were grown by physical vapor transport method with different Ce impurity content added to the SiC source material, are presented. The gradual dosage of cerium from the SiC source and continuous presence of the cerium vapor over the SiC crystallization fronts during the crystal growth processes are confirmed. The cerium influences the overall concentration of structural defects. The increase of the concentration of both, donors and acceptors, and appearance of new shallow donors (15-32 meV) in 4H-SiC crystals are observed. [ABSTRACT FROM AUTHOR]

Magneto- and piezo-spectroscopy of high quality bulk samples have been used to clarify the origin of the characteristic, V1, V2 and V3 luminescence lines observed in 6H-SiC polytypes, correspondingly, at 1.433, 1.398, and 1.368 eV. The uniaxial stress, up to 500 MPa, was applied along [11-20] and [10-10] directions, perpendicular to the c-axis of the investigated 6H-SiC crystals. Magnetic field was applied in different directions with respect to the c-axis. The obtained results allow us to analyze in detail the symmetry of the initial and final states responsible for the V2 emission line. This analysis leads to a conclusion which contradicts the existing identification of the defect responsible for this characteristic emission. [ABSTRACT FROM AUTHOR]

We report on a study of structural properties of Zn1-xCoxO by micro- and macro-Raman scattering from phonons. Bulk mixed crystals (x ≤ 0.03), grown by chemical vapour transport were investigated between 5 K and 295 K. Beside the common eigenmodes of the ZnO host lattice, we observed disorder-induced lattice vibration modes and a structure, tentatively assigned to a local vibration mode of the Co impurity. Our results are compared with literature data of other ZnO-based diluted magnetic semiconductors such as (Zn,Mn)O. [ABSTRACT FROM AUTHOR]

Raman piezospectroscopy of high quality 6H-SiC crystals is presented. The crystals used in experiments were grown by the seeded physical vapor transport method. Uniaxial stress up to 0.9 MPa, obtained using a spring apparatus, was applied along [11-20] and [10-10] directions. It was found that the application of uniaxial stress led to different energy shifts of the observed phonon excitations in the investigated 6H-SiC crystals. The obtained pressure coefficients vary in the range 0.98-5.5 cm-1 GPa-1 for different transverse optical phonon modes. For longitudinal optic phonon modes pressure coefficients in the range 1.6-3.6 cm-1 GPa-1 were found. The data obtained could be useful in evaluation of local strain fields in SiC based structures and devices including epitaxial graphene. [ABSTRACT FROM AUTHOR]

Perpendicular transport through single- and double-barrier eterostructures made up of ferromagnetic EuS layers embedded into a PbS matrix was investigated. Both resonant tunneling and probably spin filtering through EuS barrier were observed. [ABSTRACT FROM AUTHOR]