Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 25: Correlated Electrons - Poster Session
TT 25.115: Poster
Mittwoch, 29. März 2006, 14:30–18:30, P1
Polarized neutron scattering study of the spin-state transition in LaCoO3 — •M. Cwik1, M. Kriener1, M. Reuther1, L.-P. Regnault2, K. Schmalzl2, T. Lorenz1, and M. Braden1 — 1II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln — 2Institut Laue-Langevin, F-38042 Grenoble Cedex 9, France
LaCoO3 exhibits a spin state transition around 100 K which is associated with the thermal excitation of Co3+ (3d6) ions from a nonmagnetic low-spin (t2g6eg0, S=0) to a magnetic spin state without long range order [1]. The nature of this magnetic spin state is still discussed controversially. Depending on the crystal-field splitting, the intra-atomic exchange interaction and the hybridization between Co-3d and O-2p orbitals, the so-called intermediate (t2g5eg1, S=1) or the high-spin state (t2g4eg2, S=2) could be stabilized. We present an analysis of the magnetic fluctuations in LaCoO3 studied by polarized inelastic neutron scattering measurements performed on a co-mounting of six large single crystals. We find evidence for magnetic correlations in the paramagnetic phase. For a quantitative estimation of the magnetic susceptibility one needs to take these correlations into account. However, with the polarized neutrons we do not find the signal reported in reference [2] which was attributed to the LS-IS transition. In addition we present the results of inelastic neutron scattering studies on the phonon dispersion in LaCoO3.
[1] C. Zobel et al., Phys. Rev. B 66, 020402(R) (2002)
[2] Y. Kobayashi et al., cond-mat/0504351 This work is supported by the DFG through SFB 608.