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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.

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.

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

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 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.

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.

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.

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.

In this work we present a comparison of the experimental results, which have been obtained in the resonant photoemission study of electronic structure of epitaxial layers and bulk crystals of GeTe doped with Mn and/or Eu. Narrow-gap IV–VI semiconductors are known to form solid solutions not only with magnetic ions with partially filled 3d shell (e.g. Mn, Fe), but also with the elements with partially filled 4f shell (e.g. Eu, Gd). Such diluted magnetic semiconductors (DMS) exhibit transport, optical and magnetic properties attracting large interest from the point of view of basic research as well as of applications in infrared radiation sources, detectors, thermoelectric generators and, recently, spintronic devices. The ferromagnetic ordering in IV-VI –based diluted magnetic semiconductors (DMS) is governed by the Ruderman–Kittel–Yoshida–Kasuya interaction mediated by free holes related to native defects. Ge

Galvanomagnetic properties of gallium-doped Pb1−xGexTe (0.04≤x≤0.08) alloys were studied. It is shown that gallium doping induces a deep impurity level in the alloy band gap; the energy position of this level depends on the germanium content in the alloy. A model assuming that doping with gallium results in the emergence of two defect levels in the energy spectrum of the alloys is proposed.

We have studied the magnetic susceptibility and magnetization of the diluted magnetic semiconductor Pb 1 - x - y Ge x Yb y Te. The susceptibility measured is a superposition of the matrix diamagnetism, the paramagnetic contribution of electrons localized in the ytterbium-band, and the Curie-Weiss paramagnetism provided by Yb 3 + ions. The concentration of Yb 3 + ions increases monotonically with the ytterbium content, while a significant fraction of ytterbium ions remains in a nonmagnetic Yb 2 + state. This is explained within the electronic band-structure model, assuming the ytterbium-derived donor states form an impurity band in the vicinity of the valence-band top. In terms of this model the Yb 3 + concentration and electronic population of the impurity band are determined as a function of the alloy composition.

Magnetic and transport properties of Ge1−x−yMnxEuyTe crystals with chemical compositions 0.041 ≤ x ≤ 0.092 and 0.010 ≤ y ≤ 0.043 are studied. Ferromagnetic order is observed at 150

fraction of the magnetic centers increases with the increase of the Yb content, but is significantly lower than the total Ybconcentration in the investigated alloys. The obtained results are explained taking into account existing of magnetic Yb3and nonmagnetic Yb2 ions in the alloys and the possibility oftransition of ions from one state to the other due to shift of theYb impurity level with respect to the valence band edge as the composition ofthe alloy changes.Keywords: IV-VI semiconductors, magnetic ions, deep impurity levels

We report on magnetic properties and X-band electron spin resonance (ESR) study (80–430 K) of diluted magnetic semiconductors Ge1−xMnxTe (x=0.07–0.44) revealing ferromagnetism with the Curie temperature achieving 90 K. Effective magnetic moment peff per Mn2+ ion estimated from the Curie constant in the range 0.15≤x≤0.26 increases from 2.27 to 2.95 μB. The temperature evolution of ESR spectra was found to have a complicated character. We observed the presence of two distinct absorption lines of Dysonian type, associated with two resonance centers in these diluted magnetic semiconductors. Possible origin of these two lines has been analyzed and clustering effect was proposed to be most likely responsible for anomalous behavior. Anomalies in temperature dependencies of the linewidths and g-factors were observed at temperatures lower than 160 K. We connect these anomalies with magnetic fluctuations in the vicinity of transition to ferromagnetic phases. The anomalous broadening of the linewidth in paramagnetic...

The temperature and magnetic field dependencies of magnetization (T=5-340 K, B≤0.5 T) as well as electron paramagnetic resonance (EPR) (T=80-400 K) in Pb1−xCrxTe (x≤0.045) have been studied. It was shown that all samples are ferromagnetic with a clear hysteresis loop up to the room temperature and magnetic saturation moment rises with increasing of the chromium content. Using temperature dependencies of magnetization M(T) ferromagnetic Curie temperatures up to 330 K were revealed. EPR spectra in the paramagnetic phase were satisfactory approximated by a single Dysonian line. Temperature dependence of magnetic susceptibility was estimated and paramagnetic Curie temperature was determined. In ferromagnetic phase pronounced distortion and splitting of the EPR spectra on two Dysonian lines were revealed. Using approximation by the Lorenz-type curves with Dysonian terms, temperature dependencies of the main parameters for each absorption line were obtained.

Magnetic and transport properties of ferromagnetic semiconductors (FMSs) near the ferromagnetic-paramagnetic phase transition were studied in two classes of FMSs: in the III–V-based In1−xMnxSb and Ga1−xMnxAs epitaxial films and in IV–VI-based Sn1−xMnxTe and Sn1−x−yMnxEryTe alloys in bulk crystal form. Magnetoresistance data for both FMS classes are in excellent agreement with the theory of Majumdar and Littlewood, indicating that near the Curie temperature, magnetic fluctuations play a key role as scattering centers. These results also show that the Majumdar–Littlewood model can be applied to magnetically very dilute systems.

The influence of Ga doping and irradiation with high-energy electrons on the galvanomagnetic effects in n-Pb1−xGexTe:Ga (0.04≲x≲0.06) was investigated. Transitions to the metal-type conduction were found to occur both with an increase in the impurity content and as a result of irradiation. It is concluded that the impurity level does not pin the Fermi level. It is demonstrated that gallium doping and electron irradiation are the most effective complementary methods for controlling the electrical properties of alloys.