Evidence for strong orbital fluctuations below the Jahn-Teller transition in Sr$_{3}$Cr$_2$O$_8$

ORAL

Abstract

We report on the magnetic and phononic excitation spectrum of SrCrO~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 $T^{*}(=$ 125 K)$<$ $T<$ $T_{JT}(=$ 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 $T_{JT}$, but a detailed analysis of the orbital contribution to the specific heat shows the persistence of strong fluctuations down to $T^{*}$ in agreement with the IR data. Due to these fluctuations we can observe electron spin resonance absorptions only below $T^{*}$ with a linewidth \begin{math}\propto \exp{(-\Delta/k_BT)}\end{math} indicating an Orbach-type spin relaxation via the excited orbital state of the Cr $e$ doublet split by $\Delta/k_B$ = 388~K.

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Authors

  • J. Deisenhofer

    • Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany

  • Zhe Wang

    • Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany

  • M. Schmidt

    • Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany

  • A. G\&#034;{u}nther

    • Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany

  • S. Schaile

    • Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany

  • N. Pascher

    • Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany

  • F. Mayr

    • Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany

  • Y. Goncharov

    • Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany

  • H.-A. Krug von Nidda

    • Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany

  • A. Loidl

    • Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany

  • D.L. Quintero-Castro

    • Helmholtz-Zentrum Berlin f\&#034;ur Materialien und Energie, D-14109 Berlin, Germany

  • A.T.M.N. Islam

    • Helmholtz-Zentrum Berlin f\&#034;ur Materialien und Energie, D-14109 Berlin, Germany

  • B. Lake

    • Helmholtz-Zentrum Berlin f\&#034;ur Materialien und Energie, D-14109 Berlin, Germany