Dresden 2003 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 18: Metall-Isolator-Überg
änge in Quantensystemen I
TT 18.6: Vortrag
Donnerstag, 27. März 2003, 16:00–16:15, HSZ304
Effect of uniaxial stress on the Verwey transition in Fe3O4 — •H. Häffner, S. Klimm, R. Claessen, and S. Horn — Institut f. Physik, Universität Augsburg, 86159 Augsburg, Germany
Recently the occurence of charge ordering (CO) at the Verwey transition in
Fe3O4 at TV=121 K has become the subject of a controversial
discussion [1-3]. While no indication of CO has been found using resonant
X-ray scattering [1] new structural refinements have revealed 4
inequivalent B-sites and a corresponding CO state in the monoclinic phase
below TV [2]. Based on the Peierls-Hubbard model another scenario has
been proposed resulting in a bond dimerization (BD) along the quasi-1D
chains of the spinel structure [3].
We performed resistivity measurements under uniaxial stress along the cubic
[100],[110], and [111] directions. In contrast to hydrostatic compression,
which shifts TV to lower temperature, we observe an increase of TV in
all three directions. The highest slope dTV/dp is along [110], in which
BD is expected according to [3]. Under compression along [111] the
resistivity of the low temperature phase decreases rapidly with pressure
while in the other directions the resistivity remains almost constant. The
observed pressure dependence is consistent with the structural transition
as reported in [2] and is discussed within recent models of CO and BD.
This work was supported by DFG (SFB 484).
J. García et al., Phys. Rev. B 63, 054110
(2001).
J.P. Wright et al., Phys. Rev. Lett. 87, 266401
(2001).
H. Seo et al., Phys. Rev. B 65, 085107 (2002).