Spin State Transition in LaCoO3 Studied Using Soft X-ray Absorption Spectroscopy and Magnetic Circular Dichroism

Maurits W. Haverkort,1 Zhiwei Hu,1 Júlio C. Cezar2, Tobias Burnus,1 Helena Hartmann,1 Marco Reuther,1 C. Zobel,1 Thomas Lorenz,1 Arata Tanaka,3 Nicholas B. Brookes,2 Hui-Huang Hsieh,4,5 Hong-Ji Lin,5 Chien-Te Chen5 and L. Hao Tjeng1

1 II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
2 European Synchrotron Radiation Facility, Boîte Postale 220, 38043 Grenoble Cédex, France
3 Department of Quantum Matter, ADSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
4 Chung Cheng Institute of Technology, National Defense University, Taoyuan 335, Taiwan
5 National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan

[Abstract][References][Citations]

Abstract

Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-L2,3 edge we reveal that the spin state transition in LaCoO3 can be well described by a low-spin ground state and a triply-degenerate high-spin first excited state. From the temperature dependence of the spectral lineshapes we find that LaCoO3 at finite temperatures is an inhomogeneous mixed-spin- state system. It is crucial that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low-/intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance and inelastic neutron data.

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