Local electronic structure and magnetic properties of LaMn$_{0.5}$Co$_{0.5}$O$_3$ studied by x-ray absorption and magnetic circular dichroism spectroscopy
T. Burnus, Z. Hu, H. H. Hsieh, V. L. J. Joly, P. A. Joy, M. W. Haverkort, Hua Wu, A. Tanaka, H.-J. Lin, C. T. Chen, and L. H. Tjeng

We have studied the local electronic structure of LaMn$_{0.5}$Co$_{0.5}$O$_{3}$ using soft-x-ray absorption spectroscopy at the Co-$L_{3,2}$ and Mn-$L_{3,2}$ edges. We found a high-spin Co$^{2+}$--Mn$^{4+}$ valence state for samples with the optimal Curie temperature. We discovered that samples with lower Curie temperatures contain low-spin nonmagnetic Co$^{3+}$ ions. Using soft-x-ray magnetic circular dichroism we established that the Co$^{2+}$ and Mn$^{4+}$ ions are ferromagnetically aligned. We revealed also that the Co$^{2+}$ ions have a large orbital moment: $m_{\rm orb}$/$m_{\rm spin}\approx0.47$. Together with model calculations, this suggests the presence of a large magnetocrystalline anisotropy in the material and predicts a non-trivial temperature dependence for the magnetic susceptibility.

© 2008 The American Physical Society.