Large length-scale fluctuations at the spin-Peierls transition in CuGeO{sub 3}

Journal Article · Fri Dec 01 04:00:00 EST 1995 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.52.15420· OSTI ID:146699

Harris, Q J; Feng, Q; Birgeneau, R J ^[1]; Hirota, K; Shirane, G ^[2]; Hase, M; Uchinokura, K ^[3]

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1. Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
2. Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States)
3. Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113 (Japan)

We report a detailed synchrotron x-ray-scattering study of the structural fluctuations near the spin-Peierls transition in CuGeO{sub 3}. Below the transition temperature {ital T}{sub SP}, the superlattice peak profile is resolution limited and the peak intensity, which is proportional to the order parameter squared, is well described by a simple power law, (1{minus}{ital T}/{ital T}{sub SP}){sup 2{beta}}. The fitted value of {beta}, 0.33(3), agrees quantitatively with previously reported results from neutron-diffraction measurements. Above the transition temperature {ital T}{sub SP}, pretransitional lattice fluctuations are observed within about 1 K above {ital T}{sub SP}. The length scale of these fluctuations is about an order of magnitude larger than that characterizing the bulk critical fluctuations. The line shape of these large length-scale fluctuations is consistent with a Lorentzian-squared form. The measured critical exponents associated with the large length-scale fluctuations are {nu}=0.56(9), and {bar {gamma}}=2.0(3). Similar large length-scale fluctuations have been observed at the structural transitions in some perovskites and the magnetic transitions in holmium and terbium. We suggest that in CuGeO{sub 3} the large length-scale fluctuations reflect the disconnected susceptibility originating from random field Ising-type local defects.

• Research Organization: Brookhaven National Laboratory
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 146699
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 21 Vol. 52; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANTIFERROMAGNETISM
COPPER COMPOUNDS
CRITICAL TEMPERATURE
CRYSTAL-PHASE TRANSFORMATIONS
FLUCTUATIONS
GERMANATES
ORDER PARAMETERS
SYNCHROTRON RADIATION
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0013-0065 K