Dresden 2011 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 33: CE: Metal-Insulator Transition 1
TT 33.8: Vortrag
Mittwoch, 16. März 2011, 12:30–12:45, HSZ 105
Evidence for a temperature-induced spin-state transition of Co3+ in La2−xSrxCoO4 — •Nils Hollmann1, Maurits Haverkort2, Mohammed Benomar1, Matthias Cwik1, Markus Braden1, and Thomas Lorenz1 — 1II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany — 2Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, D-70569 Stuttgart, Germany
The magnetic susceptibility of mixed-valent La2−xSrxCoO4 single crystals
in a doping range of 0.5≤ x ≤ 0.8 and in a temperature range up to 1000 K is studied with the focus on the spin-state of the Co ions. The materials bear close resemblance to LaCoO3, a compound well-known for a spin-state transition of its Co3+ ions. In La2−xSrxCoO4, the magnetism below room temperature can be described by paramagnetic Co2+ in the high-spin state and Co3+ in the non-magnetic low-spin state [1]. Above room temperature, however, an increase in susceptibility compared to the behavior expected from Co2+ is seen. We attribute this rise in moment to a thermally-induced spin-state transition of Co3+, and analyze the experimental data by comparison to full-multiplet calculations for the thermal population of a higher-spin state of Co3+. We find the energy gap between the spin states being in the order of 2000 K, which hardly changes with doping. This work is supported by the SFB through SFB 608.
1] N. Hollmann et al., New Journal of Physics 10, 023018 (2008).