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Galvanomagnetic properties ( = 4.2 K, ≤ 8 T) of -Pb1-x-yGexCryTe alloys under variation of alloy composition ( x = 0.02-0.10, z = 0.01-0.03) and under pressure (P ≤ 17 kbar) have been investigated. Magnetic field dependences of the Hall coefficient H near the metal- insulator and insulator-metal transitions induced by variation of the matrix composition and pressure were obtained. In terms of the two-band conduction model, the main parameters of charge carriers were estimated. Experimental results are discussed in the framework of the diagrams of the electronic structure reconstruction, assuming a significant widening of chromium impurity band and its overlapping with the bottom of conduction band in the insulating phase.

The galvanomagnetic effects, the temperature and magnetic field dependences of mag- netization and electron paramagnetic resonance (EPR) in the Pb1-xVxTe (x ≤ 0.02) alloys under variation of the alloy composition have been investigated. Low temperature activation range of the impurity conductivity on the temperature dependences of the resistivity and the Hall coefficient has been revealed and attributed to the appearance of vanadium-induced deep level in the gap of the alloys. The magnetic susceptibility was found to be a superposition of the matrix diamagnetism and Curie-Weiss paramagnetism provided by vanadium impurity ions. EPR spectra were measured and the g-factor in the temperature range 85-200 K was obtained.

The galvanomagnetic effects ( ≤0.1 T, 4.2≤ ≤300 K) in the -Pb1-xGexTe:Cr alloys under variation of alloy composition (0.02≤x≤0.10) and under hydrostatic compression up to 17 kbar have been investigated. The metal-insulator transition under the increase of germanium content in the alloys and insulator-metal transition, induced by hydrostatic compression in Pb1-xGexTe:Cr (x=0.10) alloy, were revealed. Using the experimental data in the frame of two-band Kane dispersion relation the composition and pressure dependences of the free electron concentration and the Fermi level position were calculated. The composition and pressure coefficients of the chromium deep level movement were obtained and the models of the electronic structure reconstruction were built.

The galvanomagnetic effects in Pb1-xSnxTe: Ga under variation of alloy composition were investigated. It was found for samples with tin content x≤0.06 the temperature dependences of resistivity and the Hall coefficient have a low temperature activation range of impurity ionization, while for samples with 0.09≤x≤0.21 they have a “metallic” character. The results were discussed assuming an appearance of two different deep impurity levels EGa1 and EGa stabilizing the Fermi level in the energy spectrum. The activation energy for “insulating” samples as well as the Fermi level position for “metallic” samples were determined and used to build the energy level diagram.

We synthesize an iron-doped PbTe single-crystal ingot and investigate the phase composition and distribution of the iron impurity along the ingot as well as galvanomagnetic properties in weak magnetic fields (4.2K ≤ T ≤ 300 K, B ≤ 0.07 T) of Pb1-yFeyTe alloys. We find microscopic inclusions enriched with iron and regions with a chemical composition close to FeTe in the heavily doped samples, while the iron impurity content in the main phase rises only slightly along the length of the ingot reaching the impurity solubility limit at approximately 0.6 mol. %. Samples from the initial and the middle parts of the ingot are characterized by p-type metal conductivity. An increase of the iron impurity content leads to a decrease in the free hole concentration and to a stabilization of galvanomagnetic parameters due to the pinning of the Fermi level by the iron resonant impurity level EFe lying under the bottom of the valence band (Ev - EFe ≈ 16 meV). In the samples from the end of the ingot, a p-n inversion of the conductivity type and an increase of the free electron concentration along the ingot are revealed despite the impurity solubility limit being reached. The kinetics of changes of charge carrier concentration and of the Fermi energy along the ingot is analyzed in the framework of the six-band Dimmock dispersion relation. A model is proposed for the electronic structure rearrangement of Pb1-yFeyTe with doping, which may also be used for PbTe doped with other transition metals. [ABSTRACT FROM AUTHOR]

We synthesize a scandium-doped PbTe single-crystal ingot and investigate the phase and the elemental composition as well as galvanomagnetic properties of Pb1-yScyTe alloys in weak magnetic fields (4.2K⩽T⩽300 K, B⩽0.07 T) upon varying the scandium content (y⩽0.02). We find that all investigated samples are single-phase and n-type. The distribution of scandium impurities along the axis of the ingot is estimated to be exponential. An increase of scandium impurity content leads to a monotonous growth of the free electron concentration by four orders of magnitude (approximately from 1016 cm-3 to 1020 cm-3). In heavily doped alloys (y>0.01), the free electron concentration at the liquid-helium temperature tends to saturation, indicating the pinning of the Fermi energy by the scandium resonant impurity level located on the background of the conduction band. Using the two-band Kane and six-band Dimmock dispersion relations for IV-VI semiconductors, dependences of the Fermi energy measured from the bottom of the conduction band Ec on the scandium impurity content are calculated and the energy of the resonant scandium level is estimated to be Esc≈c+280 meV. Diagrams of electronic structure rearrangement of Pb1-yScyTe alloys upon doping are proposed. © 2014 AIP Publishing LLC. [ABSTRACT FROM AUTHOR]

The phase and elemental composition and the temperature dependences of the resistivity and Hall coefficient (temperature range 4.2 K ≤ T ≤ 300 K, magnetic fields B ≤ 0.07 T) are studied in Pb1 – x– ySnxFeyTe alloys with varying matrix composition and iron-impurity concentration along single-crystal ingots synthesized by the Bridgman–Stockbarger method. The distributions of tin and iron along ingots are obtained. Anomalous temperature dependences of the Hall coefficient related to the Fermi-level pinning by the resonance level of iron located in the valence band of the alloys are found. The experimental results are analyzed within the model of transformation of the electronic structure, involving iron level movement with respect to the top of the valence band with increasing tin concentration and temperature. The temperature coefficient of the iron level movement with respect to the midgap is determined. Possible diagrams of transformation of the electronic structure with increasing temperature in alloys with the normal spectrum (0.06 ≤ x ≤ 0.35) are proposed. [ABSTRACT FROM AUTHOR]

The field and temperature dependences of the magnetization (magnetic fields B ≤ 7.5 T, temperatures T = 2.0-75 K) of samples from a Pb1-x-ySnxVyTe (x = 0.08, y = 0.01) single-crystal ingot synthesized by the Bridgman-Stockbarger method. It is established that the sample magnetization contains two main contributions, notably, the paramagnetism of vanadium ions and diamagnetism of the crystal lattice. The field and temperature dependences of the magnetization are approximated by the sum of modified Brillouin functions corresponding to the paramagnetic contributions of vanadium in two different charge states and the diamagnetic contribution linear in terms of field. The concentrations of vanadium ions in two different magnetic states and the character of their variation along the ingot are determined within the scope of the alloy’s electronic-structure rearrangement because of doping. The results are compared with the data of X-ray fluorescence microanalysis and the results of studying the galvanomagnetic properties of the samples. [ABSTRACT FROM AUTHOR]

The field dependences of the magnetization (temperatures T = 2.0-70 K, magnetic fields B ≤ 7.5 T) of the samples from a single-crystalline Pb1 - yFeyTe ingot (y = 0.02) grown by the Bridgman method are studied. It is established that the sample magnetization contains several major contributions such as the paramagnetism of iron ions, diamagnetism of the crystal lattice, and the contributions of charge carriers and clusters of iron atoms. The field dependences of the paramagnetic contribution of iron ions and the contribution of clusters of iron atoms are approximated by theoretical dependences based on the Brillouin and Langevin functions, respectively. The average concentrations and magnetic moment of clusters as well as the total magnetic momentum of clusters in the volume unit in the samples upon increasing the impurity concentration along the ingot are determined. [ABSTRACT FROM AUTHOR]

The phase and elemental composition and magnetic properties (B ≤ 7.5 T, 2.0K ≤ T ≤ 70 K) of Pb1-yFeyTe alloys were studied under varied impurity concentration along the Bridgman-grown single-crystal ingot. The distribution of iron impurity along the length of the ingot in the main phase and the composition of microscopic inclusions of the second phase were determined. It was established that the magnetization of the samples contains several contributions: the paramagnetic contribution of impurity ions, crystal lattice diamagnetism, as well as the contributions of free charge carriers, charge carriers in the impurity band, clusters of iron ions, and the oscillating contribution of the de Haas-van Alphen effect. These contributions were systematically separated. Using an approximation for the magnetic field and temperature dependences of the impurity-ion contribution by a sum of two terms based on the modified Brillouin functions, we determined the variation of the concentration of iron ions in two different charge states along the ingot. It was shown that the charge carrier concentrations obtained from the de Haas-van Alphen oscillations are in satisfactory agreement with the Hall concentrations, indicating a weak effect of the inclusions of the second phase and magnetic clusters on homogeneity and physical properties of the main phase in Pb1-yFeyTe alloys. [ABSTRACT FROM AUTHOR]