S. Medling, Y. Lee, H. Zhang, J. F. Mitchell, J. W. Freeland, B. N. Harmon, F. Bridges
Magnetism in La$_{1-x}$Sr$_x$CoO$_3$ as a function of doping is investigated with X-ray absorption spectroscopy and X-ray magnetic circular dichroism at the O K edge, and corresponding first principles electronic structure calculations. For small x, the spectra are consistent with the formation of ferromagnetic clusters occurring within a nonmagnetic insulating matrix. Sr-induced, magnetic O-hole states form just above E$_F$ and grow with increasing Sr doping. Density functional calculations for x = 0 yield a nonmagnetic ground state with the observed rhombohedral distortion and indicates that doping introduces holes at the Fermi level in magnetic states with significant O 2p and Co t$_{2g}$ character for the undistorted pseudocubic structure. Supercell calculations show stronger magnetism on oxygen atoms having more Sr neighbors.
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http://arxiv.org/abs/1210.3396
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