Two Length Scales and Crossover Behavior in the Critical Diffuse Scattering from V2H

J. Trenkler,1 P. C. Chow,1 P. Wochner,2 H. Abe,1 K. E. Bassler,1 R. Paniago,1 H. Reichert,1 D. Scarfe,1 T. H. Metzger,3 J. Peisl,3 J. Bai,4 and S. C. Moss1

1Department of Physics, University of Houston, Houston, Texas 77204-5506 2Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 3Sektion Physik, Ludwig-Maximilians-UniversitŠt, Geschwister-Scholl-Platz 1, 80539 Mźnchen, Germany

4Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831

Phys. Rev. Lett. 81, 2276 (1998).

We have observed two length scales in a V2H crystal above the beta 1- beta 2 phase transition. A sharp Lorentzian profile in the critical diffuse scattering was superimposed on a broader one for a low-energy x-ray experiment in reflection, while no sharp component appeared in transmission at high energy. For the sharp component, we extracted tricritical exponents nu 1 and gamma 1 at small reduced temperatures t , where fluctuations are coherent over large distances. For larger t , where the correlation length is comparable to an effective defect size, there is a crossover to altered exponents.


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ab@nda.ac.jp
Department of Materials Science and Engineering
National Defense Academy

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