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M: Metallphysik

M 8: Struktur und Umwandlung III

M 8.10: Vortrag

Dienstag, 28. März 2000, 17:45–18:00, H16

Change from a Bulk Discontinuous Phase Transition in V₂H to a Continuous Transition in a Defective Skin Layer — •Johann Trenkler¹, Peter Wochner¹, Hiroshi Abe², George Reiter³, Paul Chow³, and Simon Moss³ — ¹Max-Planck-Institut fuer Metallforschung, 70569 Stuttgart — ²National Defense Academy, Yokahoma, Japan — ³University of Houston, Houston, TX 77204, USA

We have observed two length scales in the critical x-ray diffuse scattering (CDS) from a VH_0.525 crystal above the β₁-β₂ phase transition where a sharp Lorentzian profile in the CDS was superimposed on a broader one. While no sharp component appeared in transmission geometry with high-energy x-rays, no broad component was detected in an experiment confined to the defective near-surface skin layer. In this talk, we will discuss the scaling and crossover behavior of exclusively the defective skin layer or the pure bulk. We further discuss the change of the order of the phase transition from the bulk to the skin layer which is associated with a change in the sign of the fourth order term in the Landau free energy expansion.