Mercury Selenide Crystals Research Articles

New data and developments pertaining to ideas about the electron system of hybridized states of cobalt impurity atoms in a mercury selenide crystal

New experimental data on the manifestation of hybridization and spin polarization effects in 3d-states of donor electrons of a low concentration of cobalt atoms in mercury selenide crystals are obtained. The Hall concentration and mobility of conduction electrons as a function of impurity concentration, and the temperature dependences of the electron mobility, specific heat, and elastic moduli at low temperatures, are investigated. A quantitative interpretation of the observed dependences based on an earlier-developed theory in a justified simplified model of a single localization peak in the electron density of states is performed. As a result, the hybridization parameters of the cobalt states are determined by consistently fitting the observed experimental dependences, and evidence for the spontaneous spin polarization of electrons in the temperature dependences of the impurity specific heat and impurity contribution to the elastic moduli is detected.

Experimental detection of quantum oscillations of anomalous Hall resistance in mercury selenide crystals with cobalt impurities

Quantum oscillations of the anomalous component of Hall resistance with an amplitude exceeding the amplitude of the Shubnikov-de Haas oscillations of transverse magnetoresistance are observed in mercury selenide crystals doped with low concentrations of cobalt impurity. In accordance with the predictions of the Hall effect theory for systems with spontaneous spin polarization of hybridized donor electrons, the observed oscillations correspond to magnetic quantum oscillations caused by the thermodynamic anomalous Hall effect.

Thermodynamic anomalous Hall effect in quantum oscillation regime in a semiconductor with low concentration of transition element impurities

The given report is devoted to the study of anomalous Hall resistance of donor electron system of hybridized states of transition element impurities of low concentration in quantum oscillation regime. There presented theoretical description of predicted specific behaviors on the base of the ideas about thermodynamic anomalous Hall effect. In experiments on mercury selenide crystals with cobalt impurities of low concentration one revealed the quantum oscillations of anomalous contribution to the Hall resistance corresponding to the developed concepts.

Observation of Low-Temperature Softening of Transverse Elastic Modulus Due to Cobalt Impurities in Mercury Selenide

Influence on elastic moduli of donor electron d-states of cobalt impurities has been investigated in mercury selenide crystals. Experiments have been carried out at the frequency of 53 MHz in the temperature interval of 1.3–100 K. Softening of the \((C_{11} - C_{12})/2\) modulus below 10 K has been observed in the impurity crystals in contrast with the \((C_{11} + C_{12} + 2C_{44})/2\) and \(C_{44}\) moduli those have exhibited hardening at cooling typical for dielectric and semiconductor crystals. The softening of the elastic modulus has been interpreted as manifestation of hybridization of the impurity d-states in the conduction band of the crystal. Comparison of theoretical calculations with experimental data has been proved to be in good agreement and has made it possible to determine the parameters characterizing the hybridized electron states.

Manifestation of Donor Hybridized Electron States in Magnetism of Nickel Impurities in Mercury Selenide Crystals

The temperature dependences of the magnetic susceptibility χ (T) of diluted magnetic semiconductor HgSe:Ni (1·1018 < NNi < 1·1019) cm-3 were investigated. It was found that paramagnetic part of the susceptibility which is wholly due to the effect of the impurities in the range of temperature from 1.8 to 200 K is described by the Curie-Weiss law. The analysis of the concentration dependence of the Curie constant C(NNi) based on the model of the hybridized electronic states was carried out. The application of this model allowed us to determine the microscopic parameters of the electronic structure of these crystals (the effective spin of the hybridized electronic states at the nickel impurity Si and the resonance concentration of donor electrons n0d).

Anomalous Galvanomagnetic Effects due to Spontaneous Spin Polarization of Electrons in Crystal with Low Concentration of 3d-Transition Element Impurities

The results of experimental observations at room temperature of anomalous Hall effect associated with existence of a spontaneous spin polarization of conduction electrons in mercury selenide crystals doped with chromium and vanadium in the concentration range from 1·1018 to 1·1019 sm-3 are reported. Comparison of the experimental data together with the previously reported results related to crystals with iron, cobalt and nickel impurities shows that the relative contribution to the anomalous Hall effect is maximal for vanadium impurity (≈ 13%) and minimal for iron impurity (≈ 5%). Also, transverse magnetoresistance with a characteristic dependence on the magnetic field strength, on which an unusual hysteresis in the field dependence was observed, was found in investigated crystals at room temperature. Theoretical interpretation of the observed effects is developed based on the concepts of thermodynamic nature of anomalous galvanomagnetic phenomena in electron systems with spontaneous spin polarization.

Temperature anomaly of the coefficient of ultrasonic absorption by electrons of hybridized states of cobalt impurities in mercury selenide

The effects of the interaction of ultrasound with donor d electrons of cobalt impurity atoms at low concentrations in mercury selenide crystals have been investigated. The temperature dependences of the electronic contribution to the absorption coefficient at a frequency of 53 MHz in crystals with cobalt concentrations from 1018 to 1020 cm−3 and in the undoped crystal have been observed experimentally. It has been found that crystals with impurities are characterized by an anomalous nonmonotonic temperature dependence of the absorption coefficient of the slow transverse wave in a narrow temperature range near 10 K. A smooth monotonic temperature dependence has been observed for longitudinal and fast transverse waves. Based on the developed theoretical interpretation, it has been established that the anomaly in the temperature dependence of the absorption coefficient of a slow transverse wave is associated with the hybridization of impurity d states in the conduction band of the crystal. A comparison of the theoretical and experimental dependences has made it possible to determine the parameters characterizing the hybridized electronic states.

Spin ordering contribution of iron, cobalt, and nickel impurity electron states, to the low-temperature magnetic susceptibility of mercury selenide crystals

A study of the magnetic susceptibility of electron systems of hybridized states of iron, cobalt, and nickel impurities in mercury selenide crystals at low temperatures, in connection with newly discovered evidence of spontaneous spin polarization in the anomalous Hall effect, at room temperature. It is shown that in the measured paramagnetic susceptibility of electrons in hybridized states, there exists a temperature-independent portion, and that there is enough justification to identify it using spontaneous polarization. The other portion demonstrates the Curie law with decreasing temperature, and corresponds to contributions from nonpolarized electrons. Based on findings relating to the magnetization of the examined impurity systems, we identify a part of the spontaneously polarized electron density in the localized component of hybridized states. We give quantitative estimates of the aforementioned portions of each impurity.

Experimental observation of spontaneous spin polarization of electrons in hybridized states of transition element impurities in semiconductors

Experimental evidence of the possible existence of spontaneous spin polarization of the electron system in hybridized states formed by transition element impurity atoms in the conduction band of semiconducting crystals is examined. The details of a quantitative interpretation of experiments on the temperature dependence of the specific heat and elastic moduli of mercury selenide crystals with iron impurities confirm the feasibility of establishing the presence of electron spin polarization in this type of experiment, as well as the possible existence of polarization in the crystals studied here. Theoretical arguments support the observation of a thermodynamic anomalous Hall effect owing to spontaneously polarized donor electrons from low-concentration impurities.

Experimental discovery and theoretical description of the anomalous hall effect in a spontaneously polarized electron system of hybridized impurity states

An anomalous magnetic-field-independent contribution to the Hall resistance of mercury selenide crystals with a small iron impurity has been discovered in room-temperature experiments. This contribution has been shown to be due to spontaneous polarization of the electron system of hybridized impurity states. The theoretical explanation of the effect based on the thermodynamic description of dissipationless electron current in the spontaneously polarized electron system has been proposed.

Observation and interpretation of the low-temperature features of the phonon thermal conductivity of mercury selenide crystals doped with impurities of 3d transition elements

The temperature dependence of the thermal conductivity of mercury selenide containing iron and cobalt impurities is investigated experimentally. An analysis of the phonon contributions to the thermal conductivity at low temperatures in HgSe:Fe crystals reveals a significant impurity-related anomaly of the phonon thermal conductivity—a dip in its temperature dependence near 15K. On the basis of a proposed theoretical description it is shown that this anomaly is explained by the contribution to the thermal conductivity from the scattering of phonons on electrons in hybridized impurity states.

Influence of the hybridization of impurity electron states on the quantum magneto-oscillation phenomena in mercury selenide with iron impurities

Experimental study of the concentration dependence of the parameters of the Shubnikov–de Haas and de Haas–van Alphen oscillations in mercury selenide crystals containing iron impurities under conditions where the donor resonance energy level of the impurities falls into the conduction band and hybridization of the electronic states occurs. The observed concentration dependence of the Dingle temperature and g factor of the electrons exhibit minima correlated in position with the maximum of the electronic mobility. It is shown that the observed anomalies can be explained on the basis of a previously developed theory of hybridization effects.

Resonant effects in the manifestation of hybridized electronic states of iron impurities in the temperature dependences of the absorption coefficient and velocity of ultrasound propagation in mercury selenide

The temperature dependences of the absorption coefficient and phase velocity of 52-MHz ultrasonic waves in iron-doped mercury selenide crystals are studied. The presence of impurities in concentrations of about 1019 cm−3 is found to initiate the appearance of a resonance peak in the absorption coefficient at a temperature of about 5 K and the corresponding anomaly in the velocity of the slow transverse wave propagating in the 〈110〉 direction. It is shown that the observed effects can be accounted for by the interaction of ultrasound with electrons in the states created in hybridization of the iron impurity donor states with the conduction band states of the crystal. A straightforward theoretical description and quantitative interpretation of these effects are proposed and used to derive data on the hybridized states, which conform with the earlier treatment of the temperature and concentration anomalies of conductivity in the crystals under study.

Low-temperature anomalies of the mobility and Shubnikov–de Haas oscillations due to electron resonance scattering on donor impurities in semiconductors. Explanation based on the Friedel approach

Manifestations of electron resonance scattering by donor impurities in the low-temperature conductivity of semiconductors are investigated in the case when the donor resonance energy level of the impurities lies in the conduction band. It is shown that the application of resonance scattering theory in the framework of the Friedel approach can explain the stabilization of the electron density, the maximum of the electron mobility, and the minimum of the Dingle temperature as a function of the concentration of donor impurities and also the anomalous temperature dependence of the mobility due to the resonance. New experimental data are obtained on the concentration, mobility, and Dingle temperature of electrons in mercury selenide crystals containing iron impurities, and it is found that these new results, like those known previously, are in complete agreement with the behavior predicted in the proposed approach. The relation of this approach to the previous interpretation of the concentration maximum of the mobility is discussed, and arguments for its applicability are presented.

Features Peculiar to Transport Phenomena in Cobalt-Doped HgSe Crystals

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