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Heinz-Jürgen Seiffert 《Archiv der Mathematik》1995,64(2):129-131
Ohne Zusammenfassung 相似文献
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The observation of hysteresis effects in single molecule magnets like Mn12-acetate has initiated ideas of future applications in storage technology. The appearance of a hysteresis loop in such compounds is an outcome of their magnetic anisotropy. In this Letter we report that magnetic hysteresis occurs in a spin system without any anisotropy, specifically where spins mounted on the vertices of an icosahedron are coupled by antiferromagnetic isotropic nearest-neighbor Heisenberg interaction giving rise to geometric frustration. At T = 0 this system undergoes a first-order metamagnetic phase transition at a critical field Bc between two distinct families of ground state configurations. The metastable phase of the system is characterized by a temperature and field dependent survival probability distribution. 相似文献
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Jürgen Schnack Peter Hage Heinz-Jürgen Schmidt 《Journal of computational physics》2008,227(9):4512-4517
Numerically exact investigations of interacting spin systems provide a major tool for an understanding of their magnetic properties. For medium size systems the approximate Lanczos diagonalization is the most common method. In this article we suggest two improvements: efficient basis coding in subspaces and simple restructuring for openMP parallelization. 相似文献
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We investigate the dynamical behavior of finite rings of classical spin vectors interacting via nearest-neighbor isotropic exchange in an external magnetic field. Our approach is to utilize the solutions of a continuum version of the discrete spin equations of motion (EOM) which we derive by assuming continuous modulations of spin wave solutions of the EOM for discrete spins. This continuum EOM reduces to the Landau-Lifshitz equation in a particular limiting regime. The usefulness of the continuum EOM is demonstrated by the fact that the time-evolved numerical solutions of the discrete spin EOM closely track the corresponding time-evolved solutions of the continuum equation. It is of special interest that our continuum EOM possesses soliton solutions, and we find that these characteristics are also exhibited by the corresponding solutions of the discrete EOM. The robustness of solitons is demonstrated by considering cases where initial states are truncated versions of soliton states and by numerical simulations of the discrete EOM equations when the spins are coupled to a heat bath at finite temperatures. 相似文献
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Nucleophilic attack of tertiary phosphines at tellurium in R3PTe and at iodine in R3PI+ is indicated by rapid Te (or I+) transfer reactions in the systems R3PTe PR3 and R3PI+/PR3 (R = (CH3)3C, (CH3)2N). Linear intermediates of the type R3PYPR3 (Y = Te, I+) are proposed. 相似文献
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Heinz-Jürgen Voss 《Journal of Combinatorial Theory, Series B》1982,32(3):264-285
All 2-connected non-bipartite graphs are characterized which have a minimal valency ≥3 and which have no odd circuit with two or more chords. From this it is derived that in each graph with chromatic number ≥4 containing no complete 4-graph there is an odd circuit with two or more chords. This result was conjectured by P. Erdös. Corresponding results for even circuits and for circuits with a fixed edge are obtained. Some related problems of the Turán type are solved. 相似文献
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An exact formulation of the frequency interpretation of probability is proposed on the basis of G. Ludwig's concept of physical theories. Starting from a short outline of this concept, a formal definition of weak approximate reduction is developed, which covers the reduction of probability to frequency as a special case. 相似文献
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Komban R Klare JP Voss B Nordmann J Steinhoff HJ Haase M 《Angewandte Chemie (International ed. in English)》2012,51(26):6506-6510
Doped nanocrystals of NaYF(4) and NaGdF(4) are currently studied as upconversion luminescence markers and magnetic resonance imaging contrast agents. An EPR investigation on the growth mechanism of NaYF(4):Gd and NaGdF(4) nanocrystals showed that these nanomaterials grow in the standard oleic acid-based reaction medium by a dissolution/recrystallization mechanism and not by the aggregation or oriented attachment of smaller particles. 相似文献