Raman scattering is a valuable tool to investigate the magnetic excitation spectrum of quantum spin systems based on insulating transition metal oxides. Information on characteristic energy scales, dimensionality and competing interactions can be gained [1-5]. We will demonstrate experimentally that coupling a larger number of spins leads to more complex excitation spectra including magnetic bound states of singlet and triplet character up to a continuum of excitation if the ground state degeneracy is as large as in a Kagome system. In correlated electron systems also the lattice symmetry may be locally or globally be modified. We will discuss here the example of CdCr2S4, a ferromagnetic system with magneto-capacitive effects, where local distortions are proposed to lead to a very large coupling of magnetic to lattice degrees of freedom.

References:

[1] P. Lemmens, G. Güntherodt, and C. Gros, Physics Reports 375, 1-103 (2003).

[2] Spin – Orbit – Topology, a triptych, P. Lemmens and P. Millet,
in “Quantum Magnetism”, Ed. U. Schollwöck, J. Richter, B.J.J. Farell, R.F. Bishop,
Springer, Heidelberg, „Lecture Notes in Physics“,Vol. 645 (2004).

[3] Scattering: Inelastic Scattering Technique - Raman,
P. Lemmens and K.Y. Choi, in “Encyclopaedia of Condensed Matter Physics”,
Eds. G. Bassani, G. Liedl, P. Wyder, Elsevier Publishers, Amsterdam (2005).

[4] Optical Techniques for Systems with Competing Interactions,
J. Deisenhofer and P. Lemmens, in “Introduction to Highly Frustrated Magnetism”,
Eds. C. Lacroix, P. Mendels and F. Mila, Springer (New York), in print (2008).

[5] Approaching the ground state of the kagomé antiferromagnet,
W. Schweika, M. Valldor, and P. Lemmens, Phys. Rev. Lett. 98, 067201 (2007).

Acknowledgement: This work was supported by DFG and the ESF program “Highly Frustrated Magnetism” (ESF-HFM).

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/16012 must be provided.