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The effect of the presence of CeO2 in the source material on the properties of SiC crystals grown by Physical Vapor Transport (PVT) method is investigated. The doping efficiency and, indirectly, the presence of the cerium vapour in the growth atmosphere were examined by study of structural, electrical and optical properties of the crystals. X-ray photoelectron spectroscopy shows that Ce2O3 and CeO2 coexist on the SiC post-growth surfaces. A detectable Ce incorporation is observed only in the last grown part of the crystal.

We report the results of a comprehensive study of the exchange interactions in Co-doped ZnO using inelastic neutron scattering, electron paramagnetic resonance, and magnetic property measurements. In particular, we observe an unprecedentedly strong spatial anisotropy of the two nearest-neighbor exchanges, J((1)) = -25.6 +/- 0.3 K and J((2)) = -8.5 +/- 0.4 K, along with the distant-neighbor J values of ferromagnetic sign. We argue that the superexchange mechanism alone cannot account for the obtained data and we suggest that an additional mechanism leading to a strong ferromagnetic spin coupling is responsible for these findings. We also discuss the origin of this ferromagnetic mechanism.

A comprehensive experimental study on the antiferromagnetic interlayer exchange coupling in high quality epitaxial all-semiconducting EuS/PbS/EuS trilayers is reported. The influence of substrates, of the thickness of the nonmagnetic PbS spacer layer, and of temperature was investigated by means of SQUID magnetometry. In trilayers with a PbS thickness between 4 and 12 A the low temperature hysteresis loops showed the signature of antiferromagnetic coupling. The value of the interlayer exchange coupling energy was determined by simulating the data based on a Stoner-Wohlfarth model. An important observation was that the interlayer exchange coupling energy varies strongly with temperature, consistent with a power-law dependence of the exchange coupling constant on the saturation magnetization of the EuS layers. While no theoretical description is readily available, we conjecture that the observed behavior is due to a dependence of the interlayer exchange coupling energy on the exchange splitting of the EuS bands

A comprehensive experimental study on the antiferromagnetic interlayer exchange coupling in high quality epitaxial all-semiconducting EuS/PbS/EuS trilayers is reported. The influence of substrates, of the thickness of the nonmagnetic PbS spacer layer, and of temperature was investigated by means of SQUID magnetometry. In trilayers with a PbS thickness between 4 and 12 A the low temperature hysteresis loops showed the signature of antiferromagnetic coupling. The value of the interlayer exchange coupling energy was determined by simulating the data based on a Stoner-Wohlfarth model. An important observation was that the interlayer exchange coupling energy varies strongly with temperature, consistent with a power-law dependence of the exchange coupling constant on the saturation magnetization of the EuS layers. While no theoretical description is readily available, we conjecture that the observed behavior is due to a dependence of the interlayer exchange coupling energy on the exchange splitting of the EuS bands

Magnetic properties of semiconductor EuS(t)-PbS(d)-EuS(t) ferromagnetic trilayers (t=30÷300 A and d=7.5÷70 A) grown on n-type monocrystalline PbS (100) substrate were studied by SQUID magnetometry and ferromagnetic resonance technique yielding, in particular, the dependence of the ferromagnetic Curie temperature on the thickness of the EuS layer. Structural parameters of layers were examined by X-ray powder diffraction analysis. A high structural quality of the substrate and the multilayer was verified by the measurements of the X-ray rocking curve width indicating the values of the order of 100 arcsec and by atomic force microscopy revealing the presence on the cleft PbS surface regions practically flat in the atomic scale over the area of 1x0.1µm2.

Magnetic properties of semiconductor EuS(t)-PbS(d)-EuS(t) ferromagnetic trilayers (t=30÷300 A and d=7.5÷70 A) grown on n-type monocrystalline PbS (100) substrate were studied by SQUID magnetometry and ferromagnetic resonance technique yielding, in particular, the dependence of the ferromagnetic Curie temperature on the thickness of the EuS layer. Structural parameters of layers were examined by X-ray powder diffraction analysis. A high structural quality of the substrate and the multilayer was verified by the measurements of the X-ray rocking curve width indicating the values of the order of 100 arcsec and by atomic force microscopy revealing the presence on the cleft PbS surface regions practically flat in the atomic scale over the area of 1x0.1µm2.

During this project, we have developed and produced application quality photorefractive Cd(1-x)Mn(x)Te:V crystals with compositions x= 0.15, 0.45, and 0.60. These crystals are useful for applications in the wavelength range of 0.7 to 1.3mm. These crystals were obtained through the following material processing steps: (1) extensive purification of the starting elements (cadmium, manganese and tellurium) and purification if the compound (Cd(1-x)Mn(x)Te); (2) crystal growth from the melt under controlled conditions of heat and mass transfers; and (3) in situ annealing of the crystals after growth. The optimal temperature profile required to produce a favorable growth interface and minimal stress for crystals grown by the Bridgman- Stockbarger method was determined. From computational models, the temperature distribution within the solid and melt in the growth ampoule was calculated and used to construct an improved experimental system for growth of high quality Cd(1-x)Mn(x)Te:V single crystals.

We have developed and produced vanadium doped cadmium telluride (CdTe:V) crystals that exhibit the necessary properties for optical power limiting at near infrared wavelengths. The CdTe : V crystals that we have produced exhibit the field shielding effect, have good transmission of low intensity radiation and display high photoconductivity. We have demonstrated the use of these crystals for EOPL at 1.O6 micrometers. Furthermore, through device modelling and theoretical calculations, we have developed an innovative design to improve the performance of electrooptic power limiters: the two stage EOPL. A two stage EOPL could extend the range of input intensities over which the limiter can operate and improve the dynamic range by three orders of magnitude. We present the theory behind a two stage EOPL, a prototype design of this device, as well as a preliminary evaluation of its performance. A two stage EOPL device represents a new state of the art in EOPL performance. The EOPL material and device developed during this work have potential uses in both military as well as commercial applications. Commercial applications include two dimensional signal processing, increasing the dynamic range of sensors and civilian security systems.