On the experimental substantiation of the hybridization of electronic states on cobalt impurities in the conduction band of a crystal

Abstract

The article presents the experimental results concerning the role of cobalt impurities in low tem perature electrical conduction and in the Hall concentration of electrons in crystals of mercury selenide. In the limit of small concentrations of the impurities, a slow variation of the electron concentration was found as a function of impurity content, which can correspond to a donor character of the impurity d levels of cobalt atoms located in the conduction band of the host crystal under conditions of hybridization. Characteristic features have been observed in the concentration and temperature dependences of the electrical conductivity, similar to those that manifest themselves in crystals with hybridized states of iron impurities. As a result, the set of data obtained on crystals with cobalt impurities, including the previously published data on the concen tration dependence of the Curie constant and on the temperature dependence of thermopower, can be used on a qualitative level as an experimental substantiation of the previously predicted existence of two donor hybridized electron states of a cobalt impurity atom in the conduction band.

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

“…It turned out that the position of the minimum is uniquely deter mined by the position of the Fermi energy within the resonance interval (by the quantity ε 0 ), i.e., the con centration of electron donors and, hence, the concen tration of impurities. The obtained values of ε 0 in the minima for three concentrations lie in the range of 14-31 K and agree with the values corresponding to the hybridization interval according to the existing concepts [11]. The available data also agree with the obtained conclusion that the parameter Γ characteriz ing the length of the hybridization interval exceed 40 K. An important new result consists in determining the parameter γ = 0.2 K, which characterizes the relaxation frequency of the electronic system of hybridized states.…”

“…It should be noted that, in contrast to the iron impurity atom with one donor electron, the cobalt impurity atom has two donor electrons and two donor energy levels. However, the data on the temperature depen dences of different quantities indicate that the two aforementioned levels in mercury selenide crystals doped with cobalt are spaced so closely that, when dealing with such dependences, they can be consid ered as one level occupied by two electrons [11]. It is this approximation that is accepted in our work.…”

“…A simple comparison of the curves in Figs. 2 and 3 shows that the manifestation of cobalt impurities in the absorption of the given ultrasonic wave lies in the fact that the simple temperature dependence observed in the undoped crystal is superimposed by characteristic anomalies of the resonance type with a width of the order of 10 K for particular cobalt con centrations in the total temperature range of 5-20 K. It is in this temperature range that mercury selenide crystals doped with cobalt exhibited the effects associ ated with the manifestation of the hybridization of donor electronic d states of impurity atoms [10,11]. In the electronic absorption of ultrasound, the hybridiza tion effects were observed in mercury selenide crystals doped with iron [12] also in the form of sharply non monotonic anomalies (but maxima) in the tempera ture dependences of the absorption coefficient of a slow transverse wave.…”

Peculiarities of magnetic oscillations in HgSe monocrystal with Co impurities of low concentration (<1 at%)

“…1, the oscillations, at doping with Co ions, have a significantly bigger period compared with oscillations at doping with Fe ions. This difference is caused by the fact that Fermi level is located significantly lower in the first case than in the second, that corresponds with the results of the referenced studies [6,17,18,20].…”

“…It contains only one line, that in some directions is weakly split by the crystal field. Electron in the degenerated conductivity band has the resonance energy level E C ∼ 0.09 eV [20].…”