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DF: Dielektrische Festkörper
DF 13: Relaxation, Phasenübergänge
DF 13.3: Talk
Thursday, March 20, 1997, 17:00–17:20, R2
Investigations of the quantum paraelectric regime in SrTiO3 — •H. Hünnefeld1, A. Golombek1, J. Licher1, S. Kapphan1, and J.R. Schneider2 — 1Universität Osnabrück — 2HASYLAB at DESY, Hamburg
The temperature dependence of the spontaneous strain in SrTiO3 has been
studied using triple-axis diffractometers of high momentum-space
resolution for synchrotron radiation with energies ≈ 100 keV.
It is shown that the measured spontaneous strain is strongly sample
dependent, i.e. flux-grown, float-zone or Verneuil grown crystals show
differences in the spontaneous strain at 10 K of about 15%.
On the other hand only small differences are observed in samples which were
subject to different heat treatments, which change the amount of oxygen
vacancies.
In the range from 40 to 80 K the temperature dependence of the spontaneous
strain is in excellent agreement with a Landau theory taking into account
the quantum mechanical zero point fluctuations [1].
At temperatures below 40 K a difference between experimental data and theory
of about 5% occurs which is considered as an indication for a novel phase
in the quantum paraelectric regime [2].
[1] E.K.H. Salje, B. Wruck and H. Thomas, Z. Phys. B - Conden. Matter 82,399-404 (1991)
[2] K.A. M"uller, W. Berlinger and E. Tosatti, Z. Phys. B - Conden. Matter 84, 277 (1991)