Additional lines in quantum wells excitonic spectra connected with QW asymmetry caused by technology

The calculations of intensity ratio of both the main and additional lines, the energy differences between which are fulfilled for quantum well (QW) with asymmetrical potential profile, are presented here. It is grounded on the basis of this calculation that additional line in exciton spectrum of QW can be explained by transitions between the confined states of valence and conductivity electrons with different parity, which ceases to be forbidden in the presence of asymmetry of QW potential profile caused by technology of growth. It is shown that e1-hh2 additional exciton line is more intensive in most of the actual cases. In particular, it is shown that the additional exciton line, which was observed in the laser ablation grown structures with QW, may be explained as e1-hh2 transition. The calculations show the substantial sensitivity of the results not only to the parameter of widening of the interface, but to the detailed type of the interface profile function. It is concluded that the laser ablation method of heterostructure growth leads to a larger asymmetry of QW potential profile caused by technology than MBE potential profile.Проведенi розрахунки вiдношення iнтенсивностей основної i додаткової лiнiй, енергетичної вiдстанi мiж ними для квантових ям (КЯ) з асиметричним потенцiальним профiлем. Обгрунтовано, що додаткова лiнiя у екситонному спектрi КЯ може бути пояснена переходами мiж утримуваними в КЯ станами валентних електронiв i електронiв провiдностi з рiзною парнiстю, якi перестають бути забороненими у присутностi асиметрiї потенцiального профiлю, спричиненої технологiєю вирощування КЯ. Показано, що додаткова екситонна лiнiя типу e1-hh2 є бiльш iнтенсивною в бiльшiй частинi актуальних випадкiв. Зокрема, показано, що додаткова екситонна лiнiя в структурах вирощених методом лазерної абляцiї, може бути пояснена як e1-hh2 перехiд. Розрахунки показують суттєву чутливiсть не лише до параметру розширення iнтерфейсу, але й до функцiї його профiлю. Зроблено висновок, що метод лазерної абляцiї призводить до бiльшої асиметрiї КЯ, нiж метод молекулярно-пучкової епiтаксiї

Investigation of the relationship between primary production and sea ice in the Arctic seas: Assessments based on a small-component model of marine ecosystem

The work is focused on the further development of a regional coupled eco-thermohydrodynamic model of the Arctic seas with the aim of using it to better understand the interaction of dynamic and ecosystem processes in the ocean under a changing climate in the Arctic. We used the MITgcm as a thermohydrodynamic block and an original 7-component ecosystem model which includes the carbon cycle as an ocean biogeochemistry block. The results of a model climatic run for a 40-year modern period for the Arctic shelf region (Kara, Barents and White Seas) are presented. The estimates of the spatial distribution of the chlorophyll-a concentration in the surface layer have clarified the effect of sea ice on primary production in the Arctic seas, including under conditions of a changing climate that leads to a significant reduction of ice cover in the Arctic Ocean. The clear relationship between the area of the marginal ice zone and primary production has been obtained: the moments of their spring-summer peaks coincide completely and they are highly correlated (0.87), proving the importance of this zone in the functioning of the marine ecosystem. As expected, the interannual variability of the integrated primary production and the total sea ice area (both averaged over the hydrological year — from October to September) have demonstrated an antiphase oscillation which means that the reduced sea ice cover area in the previous winter is one of the main reasons for the increase in primary production in the current year

Magnetic anisotropy of epitaxial Co2Fe-Ge Heusler alloy films on MgO (100) substrates

Films of Co2Fe-Ge Heusler alloy with variable Ge concentration deposited on monocrystalline MgO (100) substrates by magnetron co-sputtering are investigated using microstructural, morphological, magnetometric, and magnetic resonance methods. The films were found to grow epitaxially, with island-like or continuous-layer morphology depending the Ge-content. The ferromagnetic resonance data versus out-of-plane and in-plane angle indicate the presence of easy plane and 4-fold in-plane anisotropy. The magnetometry data indicate additional weak 2-fold in-plane anisotropy and pronounced at low fields rotatable anisotropy. The observed magnetic anisotropy properties discussed in correlation with the microstructure and morphology of the films

On the theory of carrier-induced ferromagnetism in diluted magnetic semiconductors

Two different approaches (presented in the literature as alternative approximations) to the problem of carrier-induced ferromagnetism in the system of disordered magnetic ions of a diluted magnetic semiconductor are analyzed. They are based on a self-consistent procedure for the mean exchange fields and the RKKY interaction. Calculations in the framework of exactly solvable model are carried out, and it shows that these approaches stem from two different contributions to the magnetic susceptibility. One stems from the diagonal part of the carrier-ion exchange interaction and corresponds to mean field approximation. The other one stems from the off-diagonal part of the same interaction and describes the indirect interaction between localized spins via free carriers. These two contributions can be responsible for the different magnetic properties. Thus, the aforementioned contributions are complementary but not alternative to each other. A general approach is proposed and compared with different approximations to the problem under consideration

Anomalously large magnetostriction caused by rearrangement of magnetoelastic domains

Anomalous large values of magnetostriction related to rearrangement of multidomain state in easy-plane antiferromagnetics of iron group dihalides have been shown to be associated with magnetoelastic nature of the multidomain state. To describe that multidomain state, a parameter has been introduced which characterizes the average orientation of domains. The parameter is referred to as the domain co-alignment one.Показано, что аномально большие величины магнитострикции при перестройке многодоменного состояния легкоплоскостных антиферромагнетиков дигалидов группы железа связаны с магнитоупругой природой их многодоменного состояния. Для описания такого многодоменного состояния введен параметр, характеризующий среднюю ориентацию доменов, который обозначен как параметр сонаправленности доменов.Показано, що аномально вєликі величини магнітострикції при перебудові багатодо-менного етану легкоплощинних антиферомагнетиків дигалідів групи заліза пов’язані з магнітопружною природою їх багатодоменного етану. Для опиеу такого багатодоменно-го етану введено параметр, що характеризує еередню орієнтацію доменів, який позначено параметром епівнаправленоеті доменів