### Session X18: Focus Session: Low D/Frustrated Magnetism - Spin Chains & Ladders

2:30 PM–5:30 PM, Thursday, March 24, 2011
Room: D172

Chair: Marcelo Jamie, Los Alamos National Laboratory

Abstract ID: BAPS.2011.MAR.X18.2

### Abstract: X18.00002 : Evidence for strong orbital fluctuations below the Jahn-Teller transition in Sr$_{3}$Cr$_2$O$_8$

3:06 PM–3:18 PM

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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\"{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\"ur Materialien und Energie, D-14109 Berlin, Germany)

A.T.M.N. Islam
(Helmholtz-Zentrum Berlin f\"ur Materialien und Energie, D-14109 Berlin, Germany)

B. Lake
(Helmholtz-Zentrum Berlin f\"ur Materialien und Energie, D-14109 Berlin, Germany)

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.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.MAR.X18.2