Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique

TT 16.53: Poster

Samstag, 5. März 2005, 11:00–16:30, Poster TU C

Magnetic structure of DyBaCo₂O_5.5 — •H. Luetkens¹, H.-H. Klauss², A. Bosse², D. Cheptiakov³, S. Streule³, E. Pomjakushina³, A. Podlesnyak³, K. Conder³, and P. Lemmens⁴ — ¹Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut CH-5232 Villigen PSI, Switzerland — ²IMNF, TU Braunschweig, D-38106 Braunschweig, Germany — ³Laboratory for Neutron Scattering ETHZ & PSI, CH-5233 Villigen PSI, Switzerland — ⁴IHO, TU Braunschweig, D-38106 Braunschweig, Germany

The magnetic perovskite REBaCo₂O_5.5 system shows a rich magnetic and electronic phase diagram, with a MI transition at higher temperatures and magnetic ordering just below room temperature. Here, we report on neutron diffraction and muon spin rotation (µSR) measurements on a powder of DyBaCo₂O_5.5. From the neutron diffraction measurements an AFM (G-type) phase below 285 K is indicated by a doubling of the magnetic unit cell along both the crystallographic a and c axis. Further cooling below 260 K leads to a second magnetic phase which can be equally well described by two different spin-state ordered AFM structures. Microscopically, three magnetic transitions at 285 K, 260 K and 162 K have been observed by µSR. The high as well as the low temperature phase both show well defined muon spin precession characteristic for long range magnetic order. In the high temperature regime it was possible to independently measure the magnetic order parameter as well as the magnetic volume fraction. Additionally, at low temperatures a slowing down of the fluctuating Dy moment is observed by a characteristic peak in the longitudinal relaxation rate.