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L. Kilanski, M. Szyma«ski, B. Brodowska, M. Gorska, R. Szymczak, A. Podgorni, A. Avdonin, A. Reszka, B.J. Kowalski, V. Domukhovski , M. Arciszewska, W. Dobrowolski, V.E. Slynko and E.I. Slynko Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warszawa, Poland Faculty of Materials Engineering, Warsaw University of Technology, Woaoska 141, 02-507 Warszawa, Poland Institute of Materials Science Problems, Ukrainian Academy of Sciences, 5 Wilde Str., 274001 Chernovtsy, Ukraine

We present the studies of Sn/1-x/Cr/x/Te semimagnetic semiconductors with chemical composition x ranging from 0.004 to 0.012. The structural characterization indicates that even at low average Cr-content x < ?0.012, the aggregation into micrometer size clusters appears in our samples. The magnetic properties are affected by the presence of clusters. In all our samples we observe the transition into the ordered state at temperatures between 130 and 140 K. The analysis of both static and dynamic magnetic susceptibility data indicates that the spin-glass-like state is observed in our samples. The addition of Cr to the alloy seems to shift the spin-glass-like transition from 130 K for x = 0.004 to 140 K for x = 0.012., 4 pages, 4 figures

The influence of possible presence of Co2+ ion pairs in a bulk Zn1-xCoxO mixed crystal on the low-frequency part of the Raman spectrum is discussed. Two effects can be taken into account in the theoretical considerations when analyzing the energy level scheme corresponding to Co ions. The first is a local lattice deformation in the vicinity of Co2+ ion due to a presence of the second ion, smaller than the host ZnO lattice cation. Such deformation creates a trigonal field, which can only slightly modify the energy levels of v ion. The second effect, which results from an antiferromagnetic superexchange interaction between two Co2+ ions is responsible for a new set of energy levels. The Raman data taken at low temperature on the sample corresponding to the composition x = 0.016 demonstrated the presence of two structures at about 6 cm(-1) and 13 cm(-1). These structures may be interpreted as electronic transitions between the ground state and the first excited state of a single Co2+ ion in the substitution site of ZnO lattice and as a similar transition for Co2+ ion pair, respectively.

We present preliminary studies of magnetic and transport properties of Ge1−x−ySnxMnyTe mixed crystals with 0.091 ≤ x ≤ 0.105 and 0.012 ≤ y ≤ 0.115. Qualitative analysis of our experimental results showed the appearance of a spin-glass phase at T 10 cm−3) and low mobilities (μ < 100 cm V−1 s−1). The dependence of transport properties on the chemical composition of the samples was observed.

Nanocrystalline samples of ZnO doped with Fe2O3 were synthetized by wet chemical method. The series of ZnO nanosized samples in the wide range of Fe2O3 concentration (from 5 wt.% to 95 wt.%) was prepared by precipitation from nitrate solutions using ammonia. The phase composition of the samples was determined using X-ray diffraction measurements. The phases of hexagonal ZnO, and/or rhombohedric Fe2O3, and/or ZnFe2O4 were identified. The mean crystalline size of nanocrystals, determined with the use of Scherrer’s formula, varied from 8 to 52 nm. The preliminary micro-Raman spectroscopy measurements were performed. The observed features are typical of Fe doped ZnO nanoparticles. The magnetic measurements revealed the presence of different types of magnetic behavior. For samples with high Fe2O3 contents (above 70 wt.%) the ferromagnetic ordering was observed at room temperature. For samples with lower Fe2O3 contents we observed the phenomenon of superparamagnetism above the blocking temperature.

We present the results of low temperature annealing studies of Ga 1 - x Mn x As epilayers grown by low temperature molecular beam epitaxy in a wide range of Mn concentrations (0.01 < x < 0.084). Transport measurements in low and high magnetic fields as well as SQUID measurements were performed on a wide range of samples, serving to establish optimal conditions of annealing. Optimal annealing procedure succeeded in the Curie temperatures higher than 110 K. The highest value of the Curie temperature estimated from the maximum in the temperature dependence of zero-field resistivity (Tp) was 127 K. It is generally observed that annealing leads to large changes in the magnetic and transport properties of GaMnAs in the very narrow range of annealing temperature close to the growth temperature.

R. Kostic, N. Romcevica,∗, M. Romcevic, B. Hadžic, R. Rudolf, I. Kuryliszyn-Kudelska, W. Dobrowolski, U. Narkiewicz and D. Sibera Institute of Physics, Pregrevica 118, 11080 Belgrade, Serbia Faculty of Mechanical Engineering, University of Maribor, Smetanova 17, 2000 Maribor, Slovenia Zlatarna Celje d.d., Kresnikova 19, 3000 Celje, Slovenia Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warszawa, Poland Szczecin University of Technology, Institute of Chemical and Environment Engineering

Far-infrared and magnetic properties of Ni doped PbTe (ZNi = 1 £ 1019 at./cm3)single crystal are investigated in a broad range of temperature and magnetic elds. Far-infrared re°ection spectra were analyzed using a tting procedure based on the modi ed plasmon{two phonon interaction model. Together with the strong plasmon{two longitudinal optical phonon coupling we obtained a local mode of Ni at about 180 cmi1. This mode intensity depends on temperature. Magnetic measurements shows that PbTe alloys doped with Ni reveals weak ferromagnetic interaction between magnetic ions.

We consider theoretically the topological contribution to the anomalous Hall effect in narrow-gap IV–VI magnetic semiconductors in which the relativistic terms are relatively large and determine both the non-parabolicity of the energy spectrum and strong spin–orbit interaction. We use the relativistic Dirac model and linear response theory to calculate this contribution. Experimental data on the anomalous Hall effect in these compounds are also presented and discussed.

Two modes of electron gas injection in resonant tunnelling through GaAs/AlGaAs double-barrier heterostructures were revealed while studying their current—voltage characteristics. Examining peculiarities of the characteristics within the temperature range 4-350 K and under a high magnetic field, we were able to distinguish the contribution to resonant tunnelling of ballistic electrons mjected from a three-dimensional electron gas in the emitter contact and that of electrons injected from a two-dimensional electron gas in the accumulation layer formed near the emitter barrier.

The study of transport and of magnetic properties of Pb1-xGexTe:Yb mixed crystals (0 = x = 0.04) is reported. It is shown that Yb forms a donor state resonant with the PbTe valence band. The donor state position may be tuned (shifted relative to the energy gap) by admixture of Ge. The properties of the Yb ion in the Pb1-xGexTe matrix makes the system unique from the point of view of magnetic properties. It is demonstrated that the change of the conductivity type from p to n induces transitions from the paramagnetic state to the diamagnetic one.

We report on n-type indium doping of CdTe films grown by molecular beam epitaxy on (001) GaAs substrates. By adjusting the flux of In atoms we can precisely control the carrier concentration over three orders of magnitude — from 8 x 1014 up to 1.3 x 10 18 cm-3 . In agreement with earlier reports we confirmed that Cd overpressure plays an important role in the doping process. The doping appears to be most effective for Cd/Te pressure ratio of 1.5. For this value of Cd/Te pressure ratio essentially 100% efficiency of doping is achieved at low In concentrations (< 10 18 cm -3 ). At higher In concentrations acceptor impurities compensate shallow donors limiting the concentration of free carriers. PACS numbers: 68.55.Ln, 73.61.Ga

x Cr x Te (x < 0.009) in temperature range 3.5-300 K are presented. The obtained electron concen- tration and electron mobility vs. temperature and Cr concentration data are interpreted and discussed within the model assuming that Cr in PbTe forms a donor state resonant with the conduction band. PACS numbers: 72.20.Fr, 72.10.Fk, 72.80.Jc

Transport experiments (Hall effect and conductivity) under hydrostatic pressure up to 1 GPa at liquid helium temperatures on HgSe: Fe, Ga (NFe = 2 x 1019 cm-3 ; 0 ≤ NGa ≤ 10 19 cm-3 ) were performed. The results show that the gallium co-doping of HgSe:Fe decreases the degree of spatial correlations between charged impurities. Under the hydrostatic pressure, used as a tool for changing the ratio of the charged to neutral impurities, this effect is even more pronounced. A qualitative agreement between the calculation within the short-range correlation model and our experimental data is achieved.