• D Reznik

      Articles written in Pramana – Journal of Physics

    • Partial magnetic order in the itinerant-electron magnet MnSi

      L Pintschovius D Reznik C Pfleiderer H v Löhneysen

      More Details Abstract Fulltext PDF

      MnSi is an itinerant ferromagnet with a long-wavelength helical modulation of the spin structure. Macroscopic measurements suggest that the ordering temperatureTc is reduced with increasing pressure fromTc = 30 K atp = 0 to zero at the critical pressurepc = 14.6 kbar. Resistivity measurements show that MnSi enters a non-Fermi liquid state atpc, which remains to be understood. Neutron scattering techniques have been used to investigate the magnetic structure at and abovepc, i.e. triple-axis spectrometry and small angle neutron scattering. Surprisingly, sizeable quasi-static moments were found to survive to pressures considerably abovepc. They are, however, organized in a highly unusual way such that the magnetic Bragg reflections are sharp in the longitudinal direction but are very broad in the transverse direction, implying a partial magnetic order that was never seen before.

    • Phonon linewidths in YNi2B2C

      L Pintschovius F Weber W Reichardt A Kreyssig R Heid D Reznik O Stockert K Hradil

      More Details Abstract Fulltext PDF

      Phonons in a metal interact with conduction electrons which give rise to a finite linewidth. In the normal state, this leads to a Lorentzian shape of the phonon line. Density functional theory is able to predict the phonon linewidths as a function of wave vector for each branch of the phonon dispersion. An experimental verification of such predictions is feasible only for compounds with very strong electron–phonon coupling. YN2B2C was chosen as a test example because it is a conventional superconductor with a fairly high $T_{c}$ (15.2 K). Inelastic neutron scattering experiments did largely confirm the theoretical predictions. Moreover, they revealed a strong temperature dependence of the linewidths of some phonons with particularly strong electron–phonon coupling which can as yet only qualitatively be accounted for by theory. For such phonons, marked changes of the phonon frequencies and linewidths were observed from room temperature down to 15 K. Further changes were observed on entering into the superconducting state. These changes can, however, not be described simply by a change of the phonon linewidth.

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