The results of experimental studies of magnetoresistance oscillations are described for a HgSe monocrystal with Co impurities of low concentration (<1 at%). It has been discovered that at such impurity concentrations (~1018 cm-3) there exists two types of magnetic oscillations: Shubnikov de Haas oscillations at low temperatures (T<10 K) and magnetophonon oscillations at higher temperatures (T>10 K). The first ones are caused by the interaction of electrons with magnetic fieled inside of a Landau sublevel and the latter --- by the interaction with longitudinal optical phonons. The differences of these oscillations are characterized. A hypothesis of a nature of magnetophonon oscillations in such structures is proposed. Keywords: 3d-impurities of low concentration, zero-gap semiconductors, magnetophonon oscillations, SdH oscillations, optical and acoustic phonons.

On the single crystals of Hg1 – xFexSe (х ≤ 0.06 at %) with an extremely low concentration of the impurity iron atoms at room temperature (T = 300 K), high-temperature ferromagnetism of a new type in a impurity donor electron system was experimentally discovered.

We investigate room-temperature structural properties and spontaneous magnetism in a series of Hg1-xFexSe (0.00012 ≤ x ≤ 0.0013) diluted magnetic semiconductor bulk single crystals grown by the Bridgman method. In order to elucidate the experimentally observed high-temperature magnetism in the studied systems, the dependencies of magnetization on magnetic field strength for the entire sample series were studied. Their detailed analysis revealed impurity contributions typical of ferromagnetic materials, which are described by magnetization curves with the parameters characterizing the spontaneous spin magnetism of the donor conduction electrons of the outer d-shells of the impurity atoms. According to the previously-developed theoretical concept, such a magnetic ordering mechanism stems from the direct exchange coupling of donor conduction electrons due to hybridization of impurity states, rather than from inter-impurity interactions. The results of optical emission spectroscopy and X-ray diffraction analysis confirmed the observed ferromagnetism to be intrinsic and linked directly to the d-electrons of iron impurity atoms.

Experiments reveal a new type of high-temperature ferromagnetism in the donor impurity electron system of Hg1 − xFexSe (х ≤ 0.06 at %) single crystals with an ultralow concentration of iron impurities at room temperature (T = 300 K).

Представлены результаты экспериментального исследования осцилляций магнитосопротивления в монокристалле HgSe с примесями кобальта низкой концентрации (<1 ат%). Обнаружено, что при таких концентрациях примесей (~1018 см-3) наблюдаются два вида магнитных осцилляций: осцилляции Шубникова-де-Гааза при низких температурах (T<10 K) и магнитофононные осцилляции при температурах (T>10 K). Первые из них обусловлены взаимодействием с магнитным полем внутри подзоны Ландау, а вторые --- взаимодействием с продольными оптическими фононами. Продемонстрированы различия в свойствах этих видов осцилляций. Сделаны предположения о возможном происхождении магнитофононных осцилляций в этих структурах. Ключевые слова: магнитофононные осцилляции, осцилляции ШдГ, оптические и акустические фононы.

The given work is devoted to the experimental proof of existing the spontaneous spin polarization of the donor electron system of 3d-transition element impurity atoms of low concentration (<1 at.%) in a mercury selenide crystal. For this purpose there have been measured the dependences of the magnetization on the magnetic field strength. As a result of the analysis of the obtained dependences, there were extracted the impurity contributions, which are described by the magnetization curves typical of the ferromagnets, and by the magnetic parameters conforming to the spontaneous magnetism of the systems under study, which are unambiguously related to the donor conduction electrons of the outer d-shells of impurity atoms. By its nature, according to the developed theoretical concepts, the spontaneous spin polarization manifests itself in exchange interaction, taking place in hybridizing the electronic states of the impurity atom and the conduction band ones of the crystal.

The given work is devoted to the experimental proof of existing the spontaneous spin polarization of the donor electron system of 3d-transition element impurity atoms of low concentration (<1 at.%) in a mercury selenide crystal. For this purpose there have been measured the dependences of the magnetization on the magnetic field strength at low temperatures (T=5 K). As a result of the analysis of the obtained dependences, there were extracted the impurity contributions, which are described by the magnetization curves typical of the ferromagnets, and by the magnetic parameters conforming to the spontaneous magnetism of the systems under study, which are unambiguously related to the donor conduction electrons of the outer d-shells of impurity atoms. By its nature, according to the developed theoretical concepts, the spontaneous spin polarization manifests itself in exchange interaction, taking place in hybridizing the electronic states of the impurity atom and the conduction band ones of the crystal. Keywords: 3d-impurities of the low concentration, gapless semiconductors, hybridized electronic states, spontaneous spin polarization, low-temperature ferromagnetism

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation V. I. Okulov; XIX Ural International Winter School on Physics of Semiconductors. Low Temp. Phys. 1 January 2013; 39 (1): 1. https://doi.org/10.1063/1.4773927 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioLow Temperature Physics Search Advanced Search |Citation Search

Features of magnetic-field-dependent microwave absorption in HgSe samples doped with Co and Ni impurities in different concentrations are investigated. The electron-spin resonance spectra of weakly coupled Co atoms and peculiarities of the magnetic-absorption variation in a magnetic field passing through the zero value are established. The main parameters of the electron-spin resonance spectra and temperature and angular dependences of microwave absorption in weak fields are determined.

The electron-spin-resonance spectra of transition metal ions Fe in the HgSe matrix are analyzed. The spectra have an appearance typical of the Fe3+ ion, i.e., they consist of five fine-structure lines with a splitting that corresponds to a weak crystal field. The spectra are observed at temperatures of up to 50 K. The spectral lines are deformed and have a Dyson shape. An analysis of the temperature dependences of the line amplitudes shows that a transition from paramagnetic ordering to ferromagnetic ordering occurs with decreasing temperature, with the Curie temperature T ≈ 7 K.

AbstractThe electron-spin-resonance spectra of transition metal ions Fe in the HgSe matrix are analyzed. The spectra have an appearance typical of the Fe^3+ ion, i.e., they consist of five fine-structure lines with a splitting that corresponds to a weak crystal field. The spectra are observed at temperatures of up to 50 K. The spectral lines are deformed and have a Dyson shape. An analysis of the temperature dependences of the line amplitudes shows that a transition from paramagnetic ordering to ferromagnetic ordering occurs with decreasing temperature, with the Curie temperature T ≈ 7 K.

The results of an experimental study and theoretical description of the magnetic field dependences of the magnetization of a mercury selenide with low concentrations of iron impurities (0.01–0.2) at% at a temperature of 5 K are presented. The contributions of the spontaneous magnetism of the electron system belonging to the iron atom donor impurity hybridized states, which are shaped like saturation magnetization curves, are highlighted by performing a detailed analysis of the obtained curves. For comparative purposes, similar measurements were carried out on mercury selenide crystals without doping and with gallium impurities (0.05 at%), which allowed confirmation of the data interpretation details. Based on previously developed theoretical concepts about the electron systems under study, formulas describing the field dependences of spontaneous magnetization were obtained, and found to be in good agreement with the experimental curves. As a result of fitting the theoretical dependences to the experimental curves, the parameters characterizing the spontaneous spin magnetism of the studied impurity systems were determined; their values agree with the experimental data obtained earlier when observing Hall effect anomalies and temperature dependences of the magnetic susceptibility in the same systems.

We dedicate this paper to the memory of Victor Pavlovich Silin. The paper contains a modern formulation of the principles and main results of the quantum theory of spin waves in a conduction electron system in a crystal that does not have spontaneous spin ordering. Based on the quantum Fermi-liquid kinetic equation, we describe the propagation of electron spin oscillations in an isotropic system along the direction of a quantizing magnetic field while analyzing the dispersion equation, including the classical and quantum contributions. We present the fundamental results on quantum physics of Silin's spin waves consisting in the existence of quantum magnetic field oscillations of wave frequencies in the region, where the classical collisionless absorption is absent and new quantum spin waves appear in the transparency windows formed due to quantum suppression of classical absorption.

AbstractFeatures of magnetic-field-dependent microwave absorption in HgSe samples doped with Co and Ni impurities in different concentrations are investigated. The electron-spin resonance spectra of weakly coupled Co atoms and peculiarities of the magnetic-absorption variation in a magnetic field passing through the zero value are established. The main parameters of the electron-spin resonance spectra and temperature and angular dependences of microwave absorption in weak fields are determined.

(FIAN), an outstanding scientist, corresponding member of the Russian Academy of Sciences (RAS), professor, doctor of physico-mathematical sciences, principal research fellow of the Sector of Plasma Phenomena Theory at FIAN, professor at the Moscow Engineering Physics Institute (MEPhI), Viktor Pavlovich Silin, died on 12 January 2019. V P Silin graduated from the Physical Faculty of Lomonosov Moscow State University (MSU). His diploma thesis advisor was D I Blokhintsev. V P Silin's whole life in science was associated with the Lebedev Physical Institute, where he began working in 1949 immediately after he graduated from MSU and where he moved from junior research worker to head of the Department of Solid State Physics (1989±1995). During that time, he published over 700 scientific papers in various fields of physics. He is the author of four monographs fairly popular among specialists in plasma physics and the physics of condensed matter. The brilliant talent of Viktor Pavlovich became apparent as far back as the early 1950s, when he worked in the Department of Theoretical Physics at FIAN. Work on the development of the Tamm±Dankov method that had provided deeper insight into the nature of nuclear interactions appeared in that period. Simultaneously, he became engaged in the quantum many-body theory. Together with Yu L Klimontovich, he derived the kinetic self-consistent field equation describing a weakly ideal quantum Fermi gas. Using this equation, V P Silin predicted the existence of undamped oscillations in Fermi gas near the temperature of absolute zero. After L D Landau formulated the general theory of a Fermi liquid, these undamped oscillations were called zero sound. V P Silin also applied the Fermi-liquid theory to describe the properties of metals. The equation derived by him and known as the Landau±Silin equation became the basis of the description of collective effects in metals and allowed the prediction of cyclotron and spin waves in normal metals, a description of sound wave absorption in normal metals and conducting magnets, and the prediction of quantum spin waves. In 1970, V P Silin was awarded the USSR State Prize for the formulation of the theory of an electron Fermi liquid. Viktor Pavlovich remained interested in condensed matter physics in subsequent years. In the mid-1960s, he and P S Zyryanov conducted a large series of studies on the theory of waves in quantizing magnetic fields. These studies are well known to specialists in the field of semiconductor physics. A little later, V P Silin, together with younger disciples, developed a new approach to the description of magnetic and elastic properties of invar alloys, predicted surface quantum waves, and investigated collective excitations in ferroand antiferromagnets. One of the last areas of study in solid-state physics, to which Viktor Pavlovich had given attention till his last days, was working out the nonlocal electrodynamics of Josephson junctions and layered Josephson systems. He also obtained results of paramount importance in this area. The possibility of the existence of a whole range of new nonlinear vortex Josephson structures was predicted, the effect of quantization of Josephson vortex velocities was discovered, fast vortices were predicted, and the theory of Cherenkov radiation by vortices and vortex chains was formulated. In the late 1950s±early 1960s, V P Silin's scientific interests involved the rapidly developing plasma physics. The remarkable monograph by V P Silin and A A Rukhadze devoted to the problems of the electrodynamics of plasma and plasmalike media appeared in 1961. The monograph became a handbook for many generations of physicists and has recently been reissued. Almost immediately, a large series of papers appeared with NN Bogoliubov's ideas carried over to plasma physics. A number of new collision integrals in quantizing magnetic fields and in strong high-frequency Uspekhi Fizicheskikh Nauk 189 (5) 559 ± 560 (2019) DOI: https://doi.org/10.3367/UFNr.2019.03.038541 Translated by M V Tsaplina PERSONALIA PACS number: 01.60.+q

AbstractMagnetoresistance oscillations are considered in the case of microwave-radiation absorption in HgSe samples with a different Fe-impurity concentration. From the simultaneous analysis of the field and temperature dependences of the Shubnikov–de Haas oscillations, the effective mass, the Dingle temperature, and the quantum-limit field corresponding to the Fermi level are obtained. A method for analyzing the spectra with several oscillation frequencies, i.e., the beating effect, is proposed. The results are compared with data obtained by Hall measurements.

For the first time, magnetoresistive properties of the single crystal of HgSe with a low electron concentration were studied in wide range of temperature and magnetic field. Some fundamental parameters of spectrum and scattering of electrons were experimentally determined. Two important features of magnetic transport were found - strong transverse magnetoresistance (MR) and negative longitudinal MR, which can indicate the existence of the topological phase of the Weyl semimetal (WSM) in HgSe. Taking this hypothesis into account we suggest a modified band diagram of the mercury selenide at low electron energies. The obtained results are essential for the deeper understanding of both physics of gapless semiconductors and WSMs - promising materials for various applications in electronics, spintronics, computer and laser technologies.

A brief survey of experimental and theoretical works on the study of electronic transport and magnetic properties of iron–vanadium–aluminum alloys of composition close to Fe 2 VAl is presented. These alloys consist of “good” metals, but manifest uncommon “semiconductor-like” kinetic and thermal properties in the region of low temperatures, and an anomalous behavior of magnetic characteristics at higher temperatures. These anomalies are explained by the existence of a narrow pseudo-gap in the density of electronic states at the Fermi level E F and also by a strong effect of the processes of scattering of charge carriers by local magnetic moments.