Dresden 2011 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 35: CE: Low-dimensional Systems - Materials 3
TT 35.4: Talk
Wednesday, March 16, 2011, 14:45–15:00, HSZ 301
Evidence for strong orbital fluctuations below the Jahn-Teller transition in Sr3Cr2O8 — •Zhe Wang1, Michael Schmidt1, Axel Günther1, Sebastian Schaile1, Nikola Pascher1, Franz Mayr1, Yurri Goncharov1, Diana Quintero-Castro2, 3, A. T. M. Nazmul Islam2, Bella Lake2, 3, Hans-Albrecht Krug von Nidda1, Alois Loidl1, and Joachim Deisenhofer1 — 1Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany — 2Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109 Berlin, Germany — 3Institut für Festkörperphysik, Technische Universität Berlin, D-10623 Berlin, Germany
We report on the magnetic and phononic excitation spectrum of Sr3Cr2O8 determined by THz and infrared (IR) spectroscopy, specific heat, and electron spin resonance measurements. We identify the singlet-triplet excitations in the dimerized ground state and observe an extended temperature range 125 K < T < 285 K below the Jahn-Teller transition, where the IR active phonons change only gradually with decreasing temperature. A clear anomaly in the specific heat marks the onset of orbital ordering at 285 K, but a detailed analysis of the orbital contribution to the specific heat shows the persistence of strong fluctuations down to 125 K in agreement with the IR data. Due to these fluctuations we can observe electron spin resonance absorptions only below 125 K with a linewidth proportional to exp(-Δ/kT) indicating an Orbach-type spin relaxation via the excited orbital state of the Cr e-doublet split by Δ/k=388 K.