Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 27: CE: Poster Session

TT 27.75: Poster

Wednesday, March 24, 2010, 14:00–18:00, Poster D1

Hole induced spin polarons in LaCoO₃ — •A. Alfonsov¹, E. Vavilova^1,2, V. Kataev¹, A. Podlesnyak³, D.I. Khomskii⁴, and B. Büchner¹ — ¹IFW Dresden, D-01171 Dresden, Germany — ²Zavoisky Physical Technical Institute, RAS, 420029 Kazan, Russia — ³Oak Ridge National Laboratory, P.O. BOX 2008 MS6494 Oak Ridge TN 37831-6494, USA — ⁴II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany

We report a comparative high field electron spin- (ESR), nuclear magnetic resonance (NMR) and static magnetization study of lightly hole-doped samples of La_0.998Sr_0.002CoO₃ and La_0.998Ca_0.002CoO₃. We have shown before [1] that small Sr doping of LaCoO₃ yields the spin-state polaron with a big spin value and large spin orbital coupling. The Ca²⁺ ion, in contrast to the Sr²⁺ ion, has almost the same ionic radii as the La³⁺ ion. Therefore, the substitution of Ca for La provides mainly a hole to the system without creating a sizeable crystal field distortion around the substituted Ca ion. This difference enables us to ascertain the roles of the introduced hole and the created crystal field distortion in the formation of the spin polarons. The data obtained on Ca and Sr doped LaCoO₃ samples provide experimental evidence that the introduced hole indeed plays the main role. We discuss a model of the formation of big spin polarons in LaCoO₃ due to a very small hole doping.

[1] A. Podlesnyak et al., Phys. Rev. Lett. 101, 247603 (2008)