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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 T_V=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 T_V [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 T_V to lower temperature, we observe an increase of T_V in all three directions. The highest slope dT_V/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).
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