Dresden 2011 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 44: Poster Session Correlated Electrons
TT 44.42: Poster
Donnerstag, 17. März 2011, 10:00–13:00, P1
Orbital occupation and magnetic moments of tetrahedrally coordinated iron in CaBaFe4O7 — •Nils Hollmann1, Zhiwei Hu1,2, Hua Wu1, Martin Valldor1, Navid Qureshi1, Thomas Willers1, Yi-Ying Chin1, Julio Criginski Cezar3, Arata Tanaka4, Nicholas Brookes3, and Liu Hao Tjeng1,2 — 1II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany — 2Max Planck Institute for Chemical Physics of Solids, Nöthnitzerstr. 40, 01187 Dresden, Germany — 3European Synchrotron Radiation Facility, Boîte Postale 220, 38043 Grenoble Cédex, France — 4Department of Quantum Matter, ADSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
CaBaFe4O7 is a mixed-valent transition metal oxide having both Fe2+ and Fe3+ ions in tetrahedral coordination. Here we characterize its magnetic properties by magnetization measurements and investigate its local electronic structure using soft x-ray absorption spectroscopy at the Fe L2,3 edges, in combination with multiplet cluster calculations. We discuss the x-ray linear dichroism, finding that the Fe2+ ion in the unusual tetrahedral coordination is Jahn-Teller active with the high-spin e↑2t2↑3e↓1 configuration having a x2−y2-like electron for the minority spin. With x-ray magnetic circular dichroism it is deduced that there is an appreciable orbital moment of about Lz=0.36 caused by multiplet interactions, thereby explaining the observed magnetic anisotropy. CaBaFe4O7 might offer new opportunities to explore charge, orbital and spin physics in tetrahedrally coordinated transition metal ions. This work is supported by the SFB through SFB 608.