Valence, spin, and orbital state of Co ions in one-dimensional Ca3 Co2 O6: An x-ray absorption and magnetic circular dichroism study

International audience; We have investigated the valence, spin, and orbital state of the Co ions in the one-dimensional cobaltate Ca3 Co2 O6 using x-ray absorption and x-ray magnetic circular dichroism at the Co- L2,3 edges. The Co ions at both the octahedral Cooct and trigonal Cotrig sites are found to be in a 3+ state. From the analysis of the dichroism we established a low-spin state for the Cooct and a high-spin state with an anomalously large orbital moment of 1.7 μB at the Cotrig 3+ ions. This large orbital moment along the c -axis chain and the unusually large magnetocrystalline anisotropy can be traced back to the double occupancy of the d2 orbital in trigonal crystal field. © 2006 The American Physical Society.