1,156 research outputs found
Transformation of twinned Ni52.0Mn24.4Ga23.6 martensite in a rotating magnetic field: Theory and experiment
No full textThe influence of a rotating magnetic field on disk-shaped twinned Ni-Mn-Ga single crystals is studied theoretically and experimentally. A magnetoelastic model of ferromagnetic martensite is used for the comprehension of experimental results. The model considers the magnetic field influence on each twin component in terms of the magnetically induced mechanical stress (magnetostress). The angular dependence of magnetostress and the correspondence between the directions of the magnetic field and magnetization vector are obtained. The magnetically induced transformation of twin structure of the specimen is observed experimentally in a Ni52.0Mn24.4Ga23.6 single-crystalline disk by magnetic measurements performed in a two-dimensional vibrating sample magnetometer. The threshold character of the transformation process is stated. The threshold angles between the [100] crystallographic direction and the directions of magnetic field and magnetic vector of the transformed twin component were measured for the different magnetic field values. The comparison of experimental values with the theoretical ones points to the comparatively low value of the magnetic anisotropy constant (50 kJ m(-3)). The obtained results disclose the possibility of obtaining large magnetically induced strains in ferromagnetic-shape memory alloys with reduced magnetocrystalline anisotropy
Analysis of mechanical and magnetic instabilities in Ni-Mn-Ga single crystals
No full textAn analysis of mechanical and mechanic instabilities in Ni-Mn-Ga single crystals was carried out. Experimental stress-strain and magnetization versus field curves, measured for Ni2MnGa alloys were also compared with modeling results obtained using a statistical model. The results indicate that it is possible to evaluate the critical stress, which is necessary to overcome twin boundary pinning in a defined martensite structure
"Shall we Take off the Caps?…": Yuri Andropov and Konstantin Chernenko
No full textДанная статья является первой попыткой автора обратиться в рамках исследовательской парадигмы политической лингвистики к анализу автобиографического нарратива Ю. В. Андропова и К. У. Черненко.The given article looks at the analysis of self-portrait narrative of Yu. V. Andropov and K. U. Chernenko within the scientific paradigm of political linguistics. The aim of the study is to show the strategy of reading and comprehension of autobiography of a political leader as a communicative role act authorizing his self-consciousness and self-representation. The paper argues that the creation of a political narrative is determined by the main factor: the political leader is a diegetic narrator in the history of the country
Konstantin Ustinovich Chernenko as the Leader of the CPSU and the Soviet Union (1984—1985)
No full textThe activity of Konstantin Ustinovich Chernenko as the General Secretary of the Central Committee of the CPSU is analyzed. The author reveals the objective and subjective factors that influenced his coming to power. The relevance of the study is due to the need to obtain objective knowledge and understanding of the content of Chernenko’s internal policy at the highest post in the party. The novelty of the research lies in the fact that, based on an analysis of various historical sources, the question of which areas of the CPSU policy was focused on Chernenko’s attention as General Secretary for 13 months. It is stated that Chernenko left a noticeable mark on politics, despite the fact that he was unable to propose a policy that could be identified with his name and defined as “Chernenko’s policy”. It has been proved that he, on the whole, continued the policy pursued by Andropov, and did not seek to “freeze” the ongoing reforms. It is shown that he had a clear understanding of the need to reform not only the economy, but also some spheres of society, especially education. It is emphasized that he also raised the issue of the need to enhance the role of the Soviets. It is shown that in the top leadership of the USSR Chernenko was perceived as a temporary leader, which exacerbated the struggle for power within the Politburo
Magnetic anisotropies in Ni-Mn-Ga films on MgO(001) substrates
No full textFerromagnetic resonance was used to study the influence of temperature and film thickness on magnetic properties of Ni-Mn-Ga films deposited on single crystal MgO(001) substrates. It has been shown that depending on the film thickness and preparation condition, three configurations of magnetic anisotropy can be realized in these films. The temperature dependence of the anisotropy field is determined
Transformation behavior of Ni–Mn–Ga in the low-temperature limit
No full textThe magnetic, magnetocaloric and thermal characteristics have been studied in a Ni50.3Mn20.8Ga27.6V1.3 ferromagnetic shape memory alloy (FSMA) transforming martensitically at around 40 K. The alloy shows first a transformation from austenite to an intermediate phase and then a partial transformation to an orthorhombic martensite, all the phases being ferromagnetically ordered. The thermomagnetization dependences enabled observation of the magnetocaloric effect in the vicinity of the martensitic transformation (MT). The Debye temperature and the density of states at the Fermi level are equal to theta(D) = (276 +/- 4) K and 1.3 states = atom eV, respectively, and scarcely dependent on the magnetic field. The MT exhibited by Ni-Mn-Ga FSMAs at very low temperatures is distinctive in the sense that it is accompanied by a hardly detectable entropy change as a sign of a small driving force. The enhanced stability of the cubic phase and the low driving force of the MT stem from the reduced density of states near the Fermi level
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