Anomalous frequency and intensity scaling of collective and local modes in a coupled-spin tetrahedral system Cu2 Te2 O5 Cl2

Kwang Yong Choi, Hiroyuki Nojiri, Naresh S. Dalal, Helmuth Berger, Wolfram Brenig, Peter Lemmens

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12 Citations (Scopus)

Abstract

We report on the magnetic excitation spectrum of the coupled-spin tetrahedral system Cu2 Te2 O5 Cl2 using Raman scattering on single crystals. The transition to an ordered state at TNCl=18.2 K evidenced from thermodynamic data leads to the evolution of distinct low-energy magnetic excitations superimposed by a broad maximum. These modes are ascribed to magnons with different degree of localization and a two-magnon continuum. Two of the modes develop a substantial energy shift with decreasing temperature similar to the order parameter of other Néel ordered systems. The other two modes show only a negligible temperature dependence and dissolve above the ordering temperature in a continuum of excitations at finite energies. These observations point to a delicate interplay of magnetic intertetrahedra and intratetrahedra degrees of freedoms as expected for a system in the proximity to quantum criticality.

Original languageEnglish
Article number024416
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume79
Issue number2
DOIs
Publication statusPublished - 2009 Jan 5

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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