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Актуальність. На сьогодні вентральний цервікоспондилодез є найбільш поширеним методом хірургічної корекції більшості травматичних ушкоджень субаксіального відділу хребта. Незважаючи на широкий асортимент тілозамінних систем, у сучасній літературі відсутні дані про переваги застосування певного типу конструкцій при різних варіантах пошкодження остеолігаментозного апарата. Мета — рентгенологічна оцінка ефективності використання тілозамінностабілізуючих систем при різних варіантах травматичних ушкоджень шийного відділу хребта. Матеріали та методи. Проведено аналіз даних рентгенограм 70 пацієнтів, які перенесли вентральний субаксіальний цервікоспондилодез у зв’язку з травматичним пошкодженням шийного відділу хребта. Проведено дослідження ефективності відновлення сегментарного кіфозу оперованого сегмента і стабільності досягнутої корекції в післяопераційному періоді. Терміни спостереження: інтраопераційно, через 3–5 днів, 3, 6 і 12–18 місяців після оперативного втручання. Як система стабілізації використані комбінація «Mesh + вентральна пластина» і телескопічний тілозамінний імплант. Переломи класифіковані згідно з основними класами AOSpine subaxial cervical spine injury classification system. Результати. Інтраопераційні рентгенограми свідчать про більш дозовану корекцію сегментарного кіфозу оперованого сегмента при застосуванні тілозамінного імпланту. При цьому 87,5 % аналізованих випадків містяться в необхідному діапазоні значень. При застосуванні комбінації Mesh із вентральною пластиною цей показник становив 50 %. Аналіз динаміки втрати корекції свідчить про більшу стабільність досягнутого спондилодезу при застосуванні тілозамінного імпланту. На 3-тю — 5-ту добу післяопераційного періоду максимальне наростання сегментарного кіфозу зареєстроване при С-типі ушкодження і застосуванні комбінації Mesh із вентральною пластиною. Мінімальна деформація відзначена при використанні тілозамінного імпланту та при А-типі ушкодження. Аналогічна залежність спостерігається на всіх подальших термінах спостереження. Висновки. При виконанні вентрального субаксіального цервікоспондилодезу пошкодження типу А є найбільш стабільними, а пошкодження типу С проявляють максимальну схильність до втрати досягнутої інтраопераційної корекції. Застосування тілозамінного імпланту порівняно з комбінацією Mesh із вентральною пластиною забезпечує більше збереження сагітального контуру оперованого сегмента на всіх термінах спостереження.

Актуальність. Механічна компресія вмісту хребетного каналу, що виникає при травматичному пошкодженні хребта, має основоположне значення при визначенні тактики терапії і прогнозів регресу неврологічних розладів у постраждалих. Аналіз даних літератури демонструє відсутність критерію, який дозволяє характеризувати морфологічно гетерогенний субстрат, що викликає компресію спинного мозку. Мета: сформулювати визначення, розробити і виконати перевірку вірогідності рентгенограмметричного методу оцінки сагітального розміру різних за морфологічним типом вентрально-інтраканально розташованих травматичних субстратів. Матеріали та методи. Інформаційний пошук дозволив виявити існуючі індекси і методи вимірювання ступеня компресії хребетного каналу, а також клінічну значимість характеру і ступеня компресії спинного мозку травматичним субстратом. Для первинної перевірки вірогідності методу оцінювання вентрально розташованого травматичного субстрату був проведений ретроспективний аналіз даних нейровізуалізації 150 пацієнтів із травматичними змінами шийного відділу хребта. Були проаналізовані дані спондилограм, комп’ютерних та магнітно-резонансних томограм. Вимірювання проводились трьома незалежними експертами. Результати. Розроблений термін «компримуючий фактор», що становить собою збірне поняття і відображає загальну характеристику патологічних анатомічних субстратів, які виникають при ушкодженнях хребетного рухового сегмента, що призводять до деформації стінок хребетного каналу і, як наслідок, викликають здавлення структур хребетного каналу. Для кількісної характеристики виконувалось вимірювання сагітального розміру компримуючого фактора, що має абсолютну метричну величину і характеризує відносний ступінь зміщення субстрату в просвіт хребетного каналу. Отримані при статистичній обробці результати виявляють високу відтворюваність результатів вимірювань. Коефіцієнт конкордації становив 0,85 при р = 0,00025. Висновки. Наведену радіологічну ознаку доцільно використовувати для загальної характеристики клінічного випадку, а також при статистичній обробці даних із метою уніфікації уявлення про ступінь компресії вмісту хребетного каналу.

We present studies of the influence of the chemical composition changes on the type of magnetic order present in bulk nanocomposite Ge 1− x−y Pb x Cr y Te crystals with the average Pb-content close to x ≈ 0.20 and Cr-content, y , varying from y = 0.017 up to 0.043. Detailed magnetometric studies revealed the existence of two ordered magnetic states present in all our samples. All our crystals show a paramagnet to spin-glass-like state transition at temperatures from 135 K to 145 K, related to the presence of Cr 5 Te 8 clusters in the host lattice. The second transition type depends on the Cr-content, y . In the case of samples with y equal to 0.038 and 0.043 the ferromagnetic phase is observed with T C slightly below 70 K, while in samples with lower chromium concentration the presence of spin-glass-like state slightly below 50 K is observed. The presence of clusters in our samples has significant impact on the carrier transport and magnetotransport in our samples. The presence of critical scattering on the magnetic impurities is observed in resistivity and magnetoresistance data. Nearly-linear magnetoresistance is also observed in our samples indicating a presence of strong scattering on the grain boundaries in our samples.

We present studies of magnetotransport properties of Ge 1− x − y Pb x Mn y Te bulk crystals with chemical composition changing from 0.180 x y T SG around 90 K. The presence of strong anomalous Hall effect (AHE) with hysteresis is observed at T T SG . The data analysis allowed calculation of a correction to the Hall constant R H for T T SG and the AHE constant, R S . R S is around 10 −6 m 3 /C. R S and R H do not change strongly with temperature. The scaling law analysis has proved that the AHE in this system is due to the extrinsic mechanisms dominated by the skew scattering with relatively small contribution of the side jump process. Strong localization occurs in our system at T T SG and causes a presence of a minimum in the resistivity vs. temperature dependence. The magnetoresistance of our samples shows complex behavior at T T SG . The negative magnetoresistance is observed at T T nearly linear positive magnetoresistance is observed at temperatures from 20 K up to T ≈ T SG , where it reaches maximum. Positive linear magnetoresistance is related to the granular nature of our samples while the maximum near T SG is related to the giant spin-splitting of the valence band.

We present the studies of structural, electrical, and magnetic properties of bulk Sn 1 − x − y Cr x Eu y Te crystals with different chemical compositions varying in the range of 0.004 ≤ x ≤ 0.089 and 0.007 ≤ y ≤ 0.020. The structural characterization of our samples indicated the clustering of the Cr-ions into Cr–Te related clusters. Eu ions do not form clusters and are randomly distributed in the SnTe lattice. The magnetotransport studies show the presence of positive linear magnetoresistance with maximum amplitude of about 80% for all our samples. Positive magnetoresistance is a geometrical effect related to the presence of clusters in the SnTe lattice. The cluster-glass-like state at the temperature of about 130 K is observed for x ≤ 0.025. The cluster-glass-like state is due to the presence of Cr-rich clusters in the SnTe lattice. The ferromagnetic behavior with the Curie temperature of about 275 K is observed for the samples with x > 0.077 indicating the presence of Cr 5 Te 8 clusters in the host material. Eu ions presence in our samples shows paramagnetic behavior.

We present the studies of structural, magnetotransport, and magnetic properties of Ge1−x Eu x Te bulk crystals with the chemical composition, x, changing from 0.008 to 0.025. For the samples with x > 0.015 the sample synthesis leads to formation of Ge1−x Eu x Te spinodal decompositions with a broad range of chemical contents. The presence of Ge1−x Eu x Te spinodal decompositions is responsible for the antiferromagnetic order in our samples with x > 0.015. For the samples with x

We present studies of magnetic properties of Ge 1− x − y Pb x Mn y Te bulk crystals with chemical composition varying in the range of 0.180 x y J pd , having values from 0.47 eV to 0.80 eV gives spin-glass transition temperature, T SG , values close to the experimental values for the Ge-rich phase. The magnetic order observed for the Pb-rich phase is also due to the carrier mediated magnetic interaction. The experimental transition temperatures are fitted with J pd value ranging from 0.22 eV to 0.28 eV.

The galvanomagnetic properties in weak magnetic fields (4.2≤T≤300 K, B≤0.07 T) as well as magnetic properties (2≤T≤300 K, B≤9 T) of the single-crystal Pb1-yScyTe (y≤0.02) alloys have been investigated. We find that an increase of Sc impurity content leads to a monotonous growth of the free electron concentration (from 1016 cm-3 to 1020 cm-3). In heavily doped alloys (y>0.01), it tends to saturation, indicating the pinning of the Fermi energy by the scandium resonant level located inside the conduction band. The energy of the level is estimated (ESc≈Ec+280 meV) and the model of electronic structure rearrangement of Pb1-yScyTe alloys with doping is proposed. In the frame of this model, using experimental temperature and magnetic field dependences of magnetization, the concentrations of magnetically active scandium ions are determined and connection of the electronic structure with the magnetic properties of the alloys are discussed.

A study of the crystal structure, phase and elemental composition, and galvanomagnetic properties of transition metal (Sc, Ti, Cr, V and Fe) doped alloys, based on lead telluride and synthesized using the Bridgman method. We determined the distribution of solid solution components along the length of single-crystal ingots. It is found that the increase in the impurity leads to the appearance of regions enriched with impurity content and microscopic inclusions of compounds similar in structure to the known compounds of impurity atoms with tellurium. We found a p-n inversion of conductivity type, metal-dielectric and dielectric-metal transitions, and pinning of the Fermi level by deep impurity levels, with increasing impurity content. We compare the kinetics of changes in the concentration of free charge carriers and the Fermi energy with doping, varying matrix composition, and type of impurity. A general model for reorganizing the electron structure of the studied alloys with doping, is proposed.

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 temperature dependences of the Hall coefficient (4.2 K ≤ T ≤ 300 K, B ≤ 0.07 T) in Pb1 − x − y Ge x Cr y Te alloys (x = 0.03–0.08, y ≤ 0.01) are studied. An increase in the absolute value of the Hall coefficient with an increase in temperature is found. This fact is indicative of a decrease in the concentration of free electrons as a result of the motion of the resonant level of chromium stabilizing the Fermi level relative to the conduction-band bottom. The temperature dependences of the Hall coefficient, in satisfactory agreement with the experimental ones, are calculated in the context of the two-band Kane dispersion law allowing for the structural phase transition upon increasing temperature. The energy position and temperature coefficients of the motion of the resonant level of chromium relative to the middle of the band gap in the rhombohedral and cubic phases are determined.

Sputtering of PbTe crystals by Ar+ plasma with ion energies 50–550 eV is investigated. A dependence of sputter yields of the Te and Pb on the sputtering ion energy and sputtering time is measured. New phenomena: aperiodical oscillations of Pb and Te sputtering; a huge preference of Te sputtering reaching more than two orders of magnitude at the beginning of sputtering process; and a significant excess of Te integrated sputter yield over that of Pb for prolonged sputtering by low energy plasma at 50–160 eV, are observed. It is substantiated that these phenomena can be caused by the peculiarities of the charge states of the interstitial Pb and Te in PbTe crystal matrix and the processes of re-deposition of sputtered atoms on the sputtered surface.

The crystal structure, composition, galvanomagnetic properties in low magnetic fields (4.2 K ≤ T ≤ 300 K, B ≤ 0.07 T), and the Shubnikov–de Haas effect (T = 4.2 K, B ≤ 7 T) are studied in Pb1−x−ySnxVyTe (x = 0, 0.05–0.18) alloys synthesized by the Bridgman technique with variable vanadium impurity concentrations. It is shown that increasing the vanadium content leads to the formation of regions enriched in vanadium and of microscopic inclusions of compounds with compositions close to V3Te4. In Pb1−yVyTe stabilization of the Fermi level by a deep vanadium level, an insulator–metal transition, and a rise in the free electron concentration are observed as the vanadium content is increased. The variation in the free charge carrier concentration with increasing vanadium concentration in Pb1−yVyTe and Pb1−x−ySnxVyTe (x = 0.05–0.18) alloys is compared. Possible models for rearrangement of the electronic structure in Pb1−x−ySnxVyTe alloys with vanadium doping are discussed.

We have been studying magnetic properties of magnetic ion clusters in ternary, quaternary, and quinary IV-VI and II-IV-V 2 diluted magnetic semiconductors with varying concentrations of different magnetic and non-magnetic cations. We observed clusters of different types, from non-random distribution of magnetic ions in the host lattice to precipitates with the crystalline structure different from that of the host. The size of such precipitates varied from 200 nm to 20 μm. Depending on the type and size of clusters we observed different magnetic properties of the compounds, such as paramagnetic, spin-glass, spin-glass-like, or ferromagnetic states. For example, Zn 1-x Mn x GeAs 2 compounds with x ≤ 0.053 were paramagnetic with evidence of small short-range magnetic interactions, while in the same material with x ≥ 0.078 we observed room-temperature ferromagnetism. In IV-VI DMS clusters usually created a spin-glass or spinglass- like state. However, in some Ge 1-x-y Pb x Mn y Te crystals we observed a co-existence of two very different spin-glasslike states with transition temperatures T 1 ≈ 5 K and T 2 ≈ 90 K.

The galvanomagnetic properties in weak magnetic fields (4.2T300 K, B0.07 T) as well as Shubnikov-de Haas effect (T=4.2 K, B7 T) in the single crystal Pb1-x-ySnxVyTe (x=0.20, y0.01) under hydrostatic compression up to 15 kbar have been investigated. It is shown that under pressure the decrease of activation energy of vanadium deep level, n-p-inversion of the conductivity type at low temperatures and insulator-metal transition take place. In the metallic phase sharp increase of the Hall mobility and appearance of Shubnikov-de Haas oscillations at helium temperature are observed. The pressure coefficient of vanadium level energy is determined and the diagram of the electronic structure rearrangement for Pb1-x-ySnxVyTe under pressure is proposed.

We have studied the magnetic susceptibility, magnetization and electron paramagnetic resonance (EPR) in the diluted magnetic semiconductor Pb1-x-yMgxYbyTe. The magnetic susceptibility of this system is a superposition of the matrix diamagnetism, the paramagnetic contribution of electrons localized in the ytterbium band, and the Curie-Weiss paramagnetism provided by Yb3+ ions. The concentration of Yb3+ ions monotonically increases with the ytterbium content, while a significant fraction of ytterbium ions remains in a nonmagnetic Yb2+ state. A pronounced hyperfine structure was revealed in the EPR spectra. It was ascribed to the interaction between the electron magnetic moment of an unfilled electron shell of Yb3+ ions and nuclear magnetic moment of the 173Yb isotope. The estimated values of the effective g-factor (g1.997 0.002) and the hyperfine-interaction constant (173A=0,56 cm-1) were found to be almost independent of both alloy composition and temperature.

We report on the magnetic properties of novel diluted magnetic semiconductors Pb1 x ySnxCryTe revealing ferromagnetism at temperatures higher than room temperature. Depending on chromium concentration the Curie temperature varies in a wide range (150360 K) and effective magnetic moment achieves 1 B upon an increase of chromium doping level. Electron spin resonance (ESR) spectra in the paramagnetic phase were satisfactory approximated by a single Dysonian line. Effective g-factor tends to the saturation value g=2.080.01, while the linewidth passes through a minimum in the vicinity of magnetic ordering transition and then broadens with an increase of the temperature. In ferromagnetic phase the pronounced distortion and splitting of the ESR spectra into two lines occurs due to additional ferromagnetic contribution to absorption.

Galvanomagnetic effects in diluted magnetic semiconductors Pb 1− x − y Sn x Cr y Te at temperatures 4.2≤ T ≤300 K under variation of matrix composition ( x =0.06–0.235) and impurity content ( y =0.002–0.045) have been investigated. The p–n-conversion of the conductivity type, induced by the chromium doping, was observed. It is shown that in the heavily doped alloys temperature dependencies of resistivity and of the Hall coefficient have a “metallic” character, indicating pinning of the Fermi level by the chromium deep impurity level, situated in the conduction band. Free electron concentration and Fermi energy were calculated as functions of impurity concentration and of matrix composition by analyzing experimental data in the framework of the two-band Kane dispersion law. The impurity content coefficients of the free charge carrier concentration were determined and the diagram of electronic structure rearrangement under varying the alloy composition was obtained for the alloys under study.

The galvanomagnetic properties (T=4.2―300 K, B≤0.08T) of Pb 1―x―y Sn x V y Te alloys (x=0.06-0.26, y=0.002-0.066) have been investigated. Low temperature activation range of the impurity conductivity on the temperature dependencies of resistivity p and of the Hall coefficient R H in the heavily doped samples has been revealed and attributed to the appearance of vanadium-induced deep level in the gap of the alloys. It was found that in insulating phase alloys possess a high photosensitivity to IR excitation at temperatures up to T c ≈ 40 K. In the alloy with x ≈ 0.2 the metal-insulator transition due to the shift of the Fermi level from the valence band to the gap with the increase of the vanadium and tin content and the pinning of the Fermi level by vanadium level were observed. The diagram of electronic structure reconstruction for Pb 1 ―x―y Sn x V y Te alloys was proposed.

The electronic structure of polycrystalline Ge 0.86 Mn 0.14 Te—ferromagnetic semiconductor with T C =110 K, has been studied by means of resonant photoemission spectroscopy for photon energies close to the Mn 3p→3d excitation. The contribution of Mn 3d states to the electronic structure of the system was revealed and position of the Mn ions in the crystal, characteristic of GeTe-based diluted magnetic semiconductors was proved.

Magnetic and galvanomagnetic properties of Pb1-x-yGexCryTe (x=0.02-0.20, y=0.01-0.08) solid solutions have been investigated. It was found that the magnetic susceptibility of these alloys contains two contributions: a paramagnetic Curie-Weiss share (T

The galvanomagnetic properties of Pb 1-x-y Ge x Cr y Te in the temperature range 4.2-300 K under variation of the alloy composition (x ≤ 0.13, y ≤ 0.05) and under hydrostatic compression (P≤17 kbar) have been investigated. Pressure dependences of the electron concentration and Fermi energy were obtained. In the frame of the Kane dispersion relation theoretical dependences of electron concentration and Fermi energy were calculated and parameters of chromium impurity band were estimated. Magnetic field dependences of the Hall coefficient under variation of germanium content and under pressure were measured. It is shown, that existence of two conductivity mechanisms should be taken into account: conduction band conductivity and electron-type conductivity via chromium impurity band states. In terms of the two-band conduction model the main parameters of charge carriers were obtained. Experimental results are discussed taking into account the diagram of the electronic structure reconstruction under pressure, assuming finite capacity, electron filling and widening of the impurity band.

Magnetic properties of Pb1 − x − y Ge x Cr y Te alloys (x = 0.02–0.20, y = 0.01–0.08) were studied. It was detected that the magnetic susceptibility of alloys consists of two contributions: the paramagnetic Curie-Weiss part (the temperature region is T < 50 K) caused, probably, by the Cr3+ ion paramagnetism, and the high-temperature ferromagnetic part (T < 300 K). The dependences of the concentration of magnetic centers on the composition of the matrix were obtained from the paramagnetic and ferromagnetic contributions. It was shown that a decrease in the concentration of paramagnetic centers can be, at least qualitatively, explained by the transformation of the electronic structure as the germanium concentration increases. A phenomenological model was suggested, which explains the behavior of magnetic properties as the chromium content increases, and possible mechanisms of ferromagnetic ordering in studied alloys are discussed.

Chemical and phase composition, magnetic susceptibility, SIMS, magnetic force microscopy, and neutron diffraction data for Ge1−x−ySnxMnyTe, InSe⟨Mn⟩, and ZnO⟨Co, Mn⟩ single crystals are investigated over a wide range of temperatures and magnetic fields. For Ge1−x−ySnxMnyTe the existence of ferromagnetic (FM) ordering with a Curie temperature TC∼50K, due to an indirect exchange interaction between Mn ions via the degenerate hole gas, is established. It is shown that at T

We present the study of magnetic and transport properties of Pb(1-x-y-z)Mn(x)Sn(y)Eu(z)Te. AC magnetic susceptibility measurements as well as transport characterization were performed. The obtained results indicate that the presence of two types of magnetic ions influences magnetic properties of investigated IV-VI semimagnetic semiconductor. A qualitative analysis and possible mechanisms of the substantial dependence of the Curie temperature on the Eu content are presented. The most likely reason of the observed Curie temperature behaviour is a strong dependence of the location of a heavy mass Sigma band upon the alloy composition. The theoretical calculations in frame of simple models confirm this point.

The temperature dependence of the thermopower of Pb1−x GexTe (x = 0.01−0.05) epitaxial films grown on BaF2(111) substrates was measured. The temperature of the ferroelectric phase transition was found to disagree with that obtained for bulk single crystals of the same composition. This disagreement was explained as resulting from the effect of elastic stresses arising in the crystal lattice of the Pb1−x GexTe compound due to the difference between the thermal expansion coefficients of the film and the substrate during cooling of the layers from the growth temperature to the temperature of measurement.

The nucleation and growth of three-dimensional lead telluride (PbTe) nanoislands from vapor phase on BaF2(111) substrates strained by an external load under conditions close to thermodynamic equilibrium have been studied. Evolution of the shape of nanoislands was traced and their size distribution was statistically analyzed as dependent on the character of straining of the substrate. Homogeneous arrays of faceted PbTe nanoislands with an ultrahigh surface number density (above 1011 cm−2) and an average height of h1 ∼ 3.5 nm (at a 8–9% rms deviation) are obtained for the first time on elastoplastically strained BaF2(111) substrates under the conditions of small vapor supersaturation in the condensation zone. The formation of nanoisland arrays with such parameters is possible due to (i) the heterogeneous nucleation of PbTe nanoislands at the surface monatomic slip steps aligned in the 〈110〉 direction and (ii) the influence of straining on the kinetic processes on the substrate surface.

The impedance of single-crystal samples of PbTe(Ga) and Pb1−xGexTe(Ga) (0⩽x⩽0.095) is investigated in the frequency range from 102 to 106 Hz and temperature range 4.2–300 K. The temperature dependence of the capacitance of all the Pb1−xGexTe(Ga) samples studied exhibited two types of features. These are a pronounced peak at a temperature T=Tp, caused by a dielectric anomaly at the ferroelectric phase transition, and a characteristic strong frequency dependence of the rise in capacitance in the temperature region T 105 Hz the effect practically vanishes. This behavior of the capacitance at such low frequencies may be associated with charge exchange processes in the impurity subsystem. The experimentally determined value of Tp is substantially higher than the characteristic temperatures for the appearance of long-term relaxation processes, in particular, the delayed photoconductivity. Consequent...

The galvanomagnetic effects in new diluted magnetic semiconductors Pb $_{1-x}$ Sn x Te:Yb were studied to build the energy level diagram under variation of the alloy composition and establish the connection between the parameters of electronic structure and magnetic properties. It was found that the Hall coefficient increases almost by order of magnitude with increasing the temperature. As tin content decreases, while the ytterbium concentration grows, the hole concentration decreases by several times. The results are explained by assuming a formation of an ytterbium-induced deep defect level in the energy spectrum of the alloys, which moves up to the top of the valence band with increasing the ytterbium concentration and pins the Fermi level within the valence band at sufficiently high impurity content. The hole concentration vs. ytterbium content dependence was used to calculate the energy position of the Fermi level in the frame of two-band dispersion law and to determine the position of Yb level in the alloys. The diagram of the charge carrier energy spectrum under varying the alloy composition was built.

The effect of ytterbium impurity on the magnetic and galvanomagnetic properties of new diluted magnetic semiconductors Pb1−xSnxTe:Yb was investigated. Impurity-related Curie–Weiss paramagnetism was revealed. The concentration of magnetic centers and the ytterbium impurity-band occupancy as a function of impurity content were determined. The results are discussed assuming the formation of a ytterbium-induced level under the valence-band top and a variation of the magnetic centers concentration due to changing of the mutual arrangement of the valence band, impurity level and Fermi-level position. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have observed the negative magnetoresistance effect in the narrow-gap PbTe(Mn,Cr) semiconductor, in which the Fermi level is pinned within the gap nearby the conduction band edge. Previously the giant negative magentoresistance effect has been reported in PbTe(Mn,Yb), in which the Fermi level is pinned in the gap nearby the valence band edge. It is known that in the case of Yb doping the Fermi level pinning results from the 2+ - 3+ valence instability of an impurity. The same sort of the valence instability provides the Fermi level pinning in PbTe(Mn,Cr), but the conductivity is of the n-type, not of the p-type as in PbTe(Mn,Yb). Introduction of magnetic field leads to substantial drop of the PbTe(Mn,Cr) resistivity of about 30% at T = 4.2 K. This is however much lower than in PbTe(Mn,Yb), where the effect amplitude reached 3 orders of magnitude. The effect disappears at T = 15 K. Possible mechanisms of the effect are discussed.

In the present paper we report on results obtained by complex investigations of galvanomagnetic and magnetic properties of a diluted magnetic semiconductor Pb 1-y Yb y Te. Ytterbium doping modifies the energy spectrum of charge carriers in lead telluride by formation of deep impurity levels, moving from valence to forbidden band with increase of ytterbium content. The paramagnetic Curie-Weiss response observed has revealed a small fraction of Yb ions in magnetically active Yb 3 charge state, while the majority of impurity ions are in non-magnetic Yb 2+ state. We couple the magnetic and galvanomagnetic data in a model of charge carriers energy spectrum in Pb 1-y Yb y Te, for which energy position and electron population of the ytterbium level are derived as a function of impurity concentration.

We investigate galvanomagnetic properties and photoconductivity kinetics of Pb 1− x Ge x Te ( x ⩽0.04) alloys doped with Yb. We have found that the existence of the deep impurity level in the energy spectrum causes high photosensitivity of the alloys at temperatures under 40 K and the effect of persistent photoconductivity at helium temperature. The photoconductivity kinetics shows two types of relaxation processes: a fast one and a long-duration one. The obtained results are explained by the Jahn–Teller nature of the Yb-induced defect states. The parameters of the Jahn–Teller states are estimated.

It is expected that joint existence of ferromagnetic properties and ferroelectric structural phase transition in diluted magnetic semiconductors IV–VI leads to new possibilities of these materials. Temperature of ferroelectric transition for such crystals can be tuned by the change of Sn/Ge ratio. Magnetic susceptibility, Hall effect, resistivity and thermoelectric power of Ge 1− x − y Sn x Mn y Te single crystals grown by Bridgeman method ( x =0.083–0.115; y =0.025–0.124) were investigated within 4.2–300 K. An existence of FM ordering at T C ∼50 K probably due to indirect exchange interaction between Mn ions via degenerated hole gas was revealed. A divergence of magnetic moment temperature dependences at T ⩽ T C in field-cooled and zero-field-cooled regimes is obliged to magnetic clusters which are responsible for superparamagnetism at T > T C ≈ T f (freezing temperature) and become ferromagnetic at T C arranging spin glass state at T T f ≈ T C . Phase transition of ferroelectric type at T ≈46 K was revealed. Anomalous Hall effect which allows to determine magnetic moment was observed.

In the temperature interval 4.2–300K and magnetic fields up to 4 T, we have investigated the electrical, thermal-electrical, thermal-magnetic, and magnetic properties of single crystals of the solid solution Pb0.8Sn0.2Te. It is shown that an enhancement of its level of structural perfection leads to the appearance of a second structural phase transition (SPT), and also to an increase in the temperature of the first structural phase transition.

The photoelectric properties of Pb1−X−Y SnXGeYTe(In) epitaxial films (0.06

The purpose of this study was to investigate the magnetotransport properties of the Ge(0.743)Pb(0.183)Mn(0.074)Te mixed crystal. The results of magnetization measurements indicated that the compound is a spin-glass-like diluted magnetic semiconductor with critical temperature TSG = 97.5 K. Nanoclusters in the sample are observed. Both, matrix and clusters are magnetically active. Resistivity as a function of temperature has a minimum at 30 K. Below the minimum a variable-range hopping is observed, while above the minimum a metallic-like behavior occurs. The crystal has high hole concentration, p = 6.6E20 cm-3, temperature-independent. Magnetoresistance amplitude changes from -0.78 to 1.18% with increase of temperature. In the magnetotransport measurements we observed the anomalous Hall effect (AHE) with hysteresis loops. Calculated AHE coefficient, RS = 2.0E6 m3/C, is temperature independent. The analysis indicates the extrinsic skew scattering mechanism to be the main physical mechanism responsible for AHE in Ge(0.743)Pb(0.183)Mn(0.074)Te alloy., Comment: 4 pages, 3 figures

A study is reported of the nuclear magnetic resonance spectra of 119Sn and 125Te in SnTe with hole concentrations p77=1.42×1020−2.3×1021 cm−3 and in SnTe:Mn (NMn=0.5 and 5 at. %, p77=8×1020 cm−3) at T=4.2–300 K. Considerable broadening of NMR lines due to hyperfine magnetic interactions between nuclear and electron spins was observed in SnTe with p77>2×20 cm−3. Asymmetric broadening of the resonance lines was observed in the rhombohedral phase of SnTe and SnTe:Mn. The temperature dependence of the NMR line width of 125Te in SnTe:Mn is in agreement with the magnetic phase diagram for NMn=5 at. %. The superparamagnetic phase of SnTe:Mn is formed at T=20±2 K and the ferromagnetic phase is formed at T=4.2 K.

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.

Selective photoconductivity at frequency ω=155 cm− was discovered in PbTe(Ga) narrow-gap semiconductors at liquid-nitrogen temperatures. The corresponding energy is much lower than all characteristic energies of the electronic spectrum of the semiconductor. The effect is attributed to optical excitation of a local vibrational mode of an impurity center leading to delocalization of the electrons.

We present the experimental evidence for the presence of spinodal decomposition of the magnetic ions in the Ge/1-x-y/Cr/x/Eu/y/Te samples with chemical composition varying in the range of 0.015 < x < 0.057 and 0.003 < y < 0.042. The ferromagnetic transition at temperatures 50 < T < 57 K was observed, independent of the chemical composition. The long-range carrier mediated itinerant magnetic interactions seem to be responsible for the observed ferromagnetic order. The magnetic irreversibility with coercive field H/C/ = 5?63 mT and the saturation magnetization M/S/ 2?6 emu/g are found to strongly depend on the chemical composition of the alloy., 4 pages, 4 figures