Local electronic structure and magnetic properties of LaMn0.5Co0.5O3 studied by x-ray absorption and magnetic circular dichroism spectroscopy

T. Burnus,1 Z. Hu,1 H. H. Hsieh,2 V. L. J. Joly,3 P. A. Joy,3 M. W. Haverkort,1 Hua Wu,1 A. Tanaka,4 H.-J. Lin,5 C. T. Chen,5 and L. H. Tjeng1

1 II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
2Chung Cheng Institute of Technology, National Defense University, Taoyuan 335, Taiwan
3Physical and Materials Chemistry Division, National Chemical Laboratory, Pune 411008, India
4Department of Quantum Matter, ADSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
5National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan

[Abstract][References]

Abstract

We have studied the local electronic structure of LaMn0.5Co0.5O3 using soft-x-ray absorption spectroscopy at the Co-L3,2 and Mn-L3,2 edges. We found a high-spin Co2+–Mn4+ valence state for samples with the optimal Curie temperature. We discovered that samples with lower Curie temperatures contain low-spin nonmagnetic Co3+ ions. Using soft-x-ray magnetic circular dichroism, we established that the Co2+ and Mn4+ ions are ferromagnetically aligned. We also revealed that the Co2+ ions have a large orbital moment: morb/mspin ≈ 0.47. Together with model calculations, this suggests the presence of a large magnetocrystalline anisotropy in the material and predicts a nontrivial temperature dependence for the magnetic susceptibility.

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  64. Parameters CoO6 cluster: U3d3d = 6.5 eV, U3d2p = 8.2 eV, Δ = 5.5 eV, Tpp = 0.7 eV, ΔCFionic = 450 meV, Δt2gionic = 24.5 meV, Δzx−xy,yzionic = 5 meV, Δegionic = 88 meV, Vpdσ = −1.24 eV, Vpdπ = 0.572 eV, Hex = 6.5 meV, and Bexteff = cos 30°×1 T. Hartree-Fock results have been used for the Slater integrals, which were reduced to (Fdd2) 90%, (Fdd4) 100%, and (Fp2, Gpd1, Gpd3) 0.95%. Parameters MnO6 cluster: U3d3d = 5.0 eV, U3d2p = 6.0 eV, Δ = −3.0 eV, Tpp = 0.7 eV, ΔCFionic = 0.95 eV, Vpdσ = −1.6 eV, Vpdπ = 0.74 eV, Hex = 6.5 meV, and Bexteff = cos 30°×1 T. The Slater integrals were reduced to 70%.

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