Study on the spin-states of cobalt-based double-layer perovskite Sr2Y0.5Ca0.5Co2O7 H. He and W. Y. Zhang Eur. Phys. J. B, 61 4 (2008) 457-463 Published online: 07 March 2008 DOI: 10.1140/epjb/e2008-00100-7