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SiC crystals grown by a Physical Vapor Transport (PVT) method in the presence of varying Ce impurity contents (from 0.1 wt% up to 2.5 wt%) added to SiC source material are investigated. The presence of the cerium vapor in the growth atmosphere is confirmed by X-ray photoelectron spectroscopy measurements. Different electrical properties of SiC crystals are obtained while use was made of non-oxide (CeSi2) or oxide (CeO2) sources of Ce impurity. The impact of cerium on low concentrations of boron atoms in bulk SiC is reported. Presence of Ce in the vapor stabilizes the growth of the 4H-SiC polytype. [ABSTRACT FROM AUTHOR]

We present the studies of structural, magnetic, and magnetotransport properties of Cd1-x-y Mnx Zny SnAs2 crystals with the average Mn contents x changing from 0.013 to 0.170 and Zn contents y varying from 0.002 to 0.051. Homogenous distribution of Mn ions is observed for the samples with x = 0.025. The presence of Mn As clusters in the studied alloy for x > 0.025 induces room-temperature ferromagnetism with the Curie temperature TC, with values around 325K. High crystal quality leads to high carrier mobility values observed for all of our samples, as high as 7100 cm²/(Vs) for x = 0.025 and y = 0.028. The Shubnikov-de Haas oscillations are observed at T = 50 K for all of our samples. The oscillations allowed the calculation of the effective mass m*, giving values of about 0.11-0.12me. The presence of magnetic impurities has a strong influence on the magnetoresistance of the alloy. For the samples with x = 0.076, the Shubnikov-de Haas oscillations are observed on the background of a strong linear positive magnetoresistance, present up to room temperature. The maximum values of the linear positive magnetoresistance are close to 200% for the sample with x = 0.170 and y = 0.002, at T = 1.5K. This positive magnetoresistance is related to the presence of Mn As clusters in the semiconductor lattice. [ABSTRACT FROM AUTHOR]

Depopulation of the Mn2+ state in ZnO:Mn upon illumination, monitored by quenching of the Mn2+ EPR signal intensity, was observed at temperatures below 80 K. Mn2+ photoquenching is shown to result from the Mn2+→Mn3+ ionization transition, promoting one electron to the conduction band. Temperature dependence of this process indicates the existence of an energy barrier for electron recapture of the order of 1 meV. GGA+U calculations show that after ionization of Mn2+ a moderate breathing lattice relaxation in the 3+ charge state occurs, which increases energies of d(Mn) levels. At its equilibrium atomic configuration, Mn3+ is metastable since the direct capture of photoelectron is not possible. The metastability is mainly driven by the strong intrashell Coulomb repulsion between d(Mn) electrons. Both the estimated barrier for electron capture and the photoionization energy are in good agreement with the experimental values. [ABSTRACT FROM AUTHOR]

Room-temperature laser action from Cr(2+)-doped Cd(0.85)Mn(0.15)Te has been demonstrated for what is believed to be the first time. We achieved pulsed laser operation centered at ~2.5mu m by pumping into the mid-infrared absorption band of Cr(2+) ions by use of the 1.907- mum output of a H(2) Raman-shifted Nd:YAG laser. The output of the free-running Cr(2+):Cd(0.85)Mn(0.15)Te laser had a width of ~50 nm (FWHM), and the slope efficiency was calculated to be 5.5% under nonoptimum conditions.