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Phys. Rev. B 72, 094434 (2005) [8 pages]

Magnetic excitations in the weakly coupled spin dimers and chains material Cu2Fe2Ge4O13

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T. Masuda*, A. Zheludev, and B. Sales
Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393, USA

S. Imai† and K. Uchinokura‡
Department of Advanced Materials Science, The University of Tokyo, 5-1-5, Kashiwa-no-ha, Kashiwa 277-8581, Japan

S. Park§
NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA

Received 2 June 2005; revised 8 August 2005; published 28 September 2005

Magnetic excitations in a weakly coupled spin dimers and chains compound Cu2Fe2Ge4O13 are measured by inelastic neutron scattering. Both structure factors and dispersion of low-energy excitations up to 10 meV energy transfer are well described by a semiclassical spin wave theory involving interacting Fe3+(S=5∕2) chains. Additional dispersionless excitations are observed at higher energies, at ℏω=24 meV, and associated with singlet-triplet transitions within Cu2+ dimers. Both types of excitations can be understood by treating weak interactions between the Cu2+ and Fe3+ subsystems at the level of the mean-field random phase approximation. However, this simple model fails to account for the measured temperature dependence of the 24 meV mode.

© 2005 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.72.094434
DOI:
10.1103/PhysRevB.72.094434
PACS:
75.10.Jm, 75.25.+z, 75.50.Ee

*Present address: International Graduate School of Arts and Sciences, Yokohama City University, 22-2, Seto, Kanazawa-ku, Yokohama city, Kanagawa, 236-0027, Japan. Electronic address: tmasuda@yokohama-cu.ac.jp

†Present address: Semiconductor R & D Center, Yokohama R & D Laboratories, The Furukawa Electric Co., Ltd., Japan.

‡Present address: The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan.

§Present address: HANARO Center, Korea Atomic Energy Research Institute, Daejeon, South Korea.

 
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