Ferromagnetism in magnetically doped III-V semiconductors

The origin of ferromagnetism in semimagnetic III-V materials is discussed. The indirect exchange interaction caused by virtual electron excitations from magnetic impurity level in the bandgap to the valence band can explain ferromagnetism in GaAs(Mn) no matter samples are degenerated or not. Formation of ferromagnetic clusters and percolation picture of phase transition describes well all available experimental data and allows to predict the Mn-composition dependence of transition temperature in wurtzite (Ga,In,Al)N epitaxial layers.Comment: 4 pages with 3 figure

Polaron percolation in diluted magnetic semiconductors

We theoretically study the development of spontaneous magnetization in diluted magnetic semiconductors as arising from a percolation of bound magnetic polarons. Within the framework of a generalized percolation theory we derive analytic expressions for the Curie temperature and the magnetization, obtaining excellent quantitative agreement with Monte Carlo simulation results and good qualitative agreement with experimental results.Comment: 5 page

Метрологическое образование в России: итоги и перспективы

The main purposes of education and training of metrological experts based on brief review of key development stages of metrological education system were underlined. The alternate version of integration of science and education, when learning activities are realising at state scientific metrological centres was suggested. There was showed that the creation of metrological cluster for providing the education is effectually. Such clusters should consist of universities, scientific metrological institutes as well as high-schools. For the realisation of uniformity of preparation and training of potential experts on the all stages of «educational stairs» was suggested the way based on development of united teaching and learning materials on methodological support.В статье кратко рассмотрены основные этапы развития системы метрологического образования в России, выделены основные задачи при подготовке специалистов-метрологов. Предложен альтернативный вариант интеграции образования и науки при осуществлении образовательной деятельности в Государственных научных метрологических центрах. Показано, что для проведения обучения целесообразно создание метрологических кластеров. В состав кластеров предлагается включать университеты, научные метрологические институты и общеобразовательные школы. Для реализации единообразия в подготовке будущих метрологов на всех этапах образовательной пирамиды предложен подход, основанный на разработке единого учебно-методического обеспечения

Comparison of electromagnetic and nuclear dissociation of 17Ne^{17}\mathrm{Ne}

The Borromean drip-line nucleus ¹⁷Ne has been suggested to possess a two-proton halo structure in its ground state. In the astrophysical rp-process, where the two-proton capture reaction ¹⁵O(2p,γ) ¹⁷Ne plays an important role, the calculated reaction rate differs by several orders of magnitude between different theoretical approaches. To add to the understanding of the ¹⁷Ne structure we have studied nuclear and electromagnetic dissociation. A 500 MeV/u¹⁷Ne beam was directed toward lead, carbon, and polyethylene targets. Oxygen isotopes in the final state were measured in coincidence with one or two protons. Different reaction branches in the dissociation of ¹⁷Ne were disentangled. The relative populations of s and d states in ¹⁶F were determined for light and heavy targets. The differential cross section for electromagnetic dissociation (EMD) shows a continuous internal energy spectrum in the three-body system ¹⁵O + 2p. The ¹⁷Ne EMD data were compared to current theoretical models. None of them, however, yields satisfactory agreement with the experimental data presented here. These new data may facilitate future development of adequate models for description of the fragmentation process