1,857 research outputs found

    Liquid antiferromagnets in two dimensions

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    It is shown that, for proper symmetry of the parent lattice, antiferromagnetic order can survive in two-dimensional liquid crystals and even isotropic liquids of point-like particles, in contradiction to what common sense might suggest. We discuss the requirements for antiferromagnetic order in the absence of translational and/or orientational lattice order. One example is the honeycomb lattice, which upon melting can form a liquid crystal with quasi-long-range orientational and antiferromagnetic order but short-range translational order. The critical properties of such systems are discussed. Finally, we draw conjectures for the three-dimensional case.Comment: 4 pages RevTeX, 4 figures include

    О наведенной активности при дефектоскопии толстых стальных изделий с помощью тормозного излучения бетатрона

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    В статье рассматривается образование наведенной активности в стальных изделиях в результате возникновения фотоядерных реакций на изотопах элементов, входящих в состав сталей при дефектоскопии изделий тормозным излучением бетатрона с максимальной энергией Е? = 30-35 Мэв. Определяются мощности доз ? и ?-излучений радиоактивных изотопов вблизи поверхности изделий. Проведены результаты экспериментального определения наведенной активности в стали

    Doping dependence of the Neel temperature in Mott-Hubbard antiferromagnets: Effect of vortices

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    The rapid destruction of long-range antiferromagnetic order upon doping of Mott-Hubbard antiferromagnetic insulators is studied within a generalized Berezinskii-Kosterlitz-Thouless renormalization group theory in accordance with recent calculations suggesting that holes dress with vortices. We calculate the doping-dependent Neel temperature in good agreement with experiments for high-Tc cuprates. Interestingly, the critical doping where long-range order vanishes at zero temperature is predicted to be xc ~ 0.02, independently of any energy scales of the system.Comment: 4 pages with 3 figures included, minor revisions, to be published in PR

    Correlated defects, metal-insulator transition, and magnetic order in ferromagnetic semiconductors

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    The effect of disorder on transport and magnetization in ferromagnetic III-V semiconductors, in particular (Ga,Mn)As, is studied theoretically. We show that Coulomb-induced correlations of the defect positions are crucial for the transport and magnetic properties of these highly compensated materials. We employ Monte Carlo simulations to obtain the correlated defect distributions. Exact diagonalization gives reasonable results for the spectrum of valence-band holes and the metal-insulator transition only for correlated disorder. Finally, we show that the mean-field magnetization also depends crucially on defect correlations.Comment: 4 pages RevTeX4, 5 figures include
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