Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 22: Low-dimensional Systems - Materials
TT 22.7: Vortrag
Donnerstag, 29. März 2007, 11:00–11:15, H18
Optical properties of the 1D antiferromagnet KCuF3 — •Joachim Deisenhofer1, Paolo Ghigna2, Franz Mayr3, Alois Loidl3, and Dirk van der Marel1 — 1Departement de Physique de la Matiere Condensee, Universite de Geneve, CH-1211 Geneve 4, Switzerland, — 2Dipartimento di Chimica Fisica, Universita di Pavia, I-27100 Pavia, Italy, — 3Experimentalphysik V, Center for Electronic Correlations and Magnetism, Augsburg University, D-86135 Augsburg, Germany
We present measurements of the optical properties of KCuF3, a paradigm for orbital ordering[1] and one of the best realizations of a quasi-one dimensional spin chain [2]. We can identify the d-d excitations on the Cu sites and the charge-transfer gap of the system. The observed level splitting and the gap value will be compared to recent results obtained by LDA+U calculations [3]. Moreover, we find anomalies in the optical properties already above the magnetic phase transition. These features appear concomitantly with a change in the orbital order parameter as reported by resonant x-ray scattering [4] and evidence a low-temperture structural change [5].
[1] K. I. Kugel and D. I. Khomskii, Sov. Phys. Usp. 25, 231 (1982). [2] B. Lake et al., Nature Materials 4, 329 (2005). [3] I. Leonov, unpublished. [4] L. Paolasini et al., PRL 88, 106403 (2002). [5] N. Binggeli and M. Altarelli, PRB 70, 085117 (2004).