X-ray absorption and x-ray magnetic dichroism study on Ca3CoRhO6 and Ca3FeRhO6

By using x-ray absorption spectroscopy at the Rh L-2,L-3, Co L-2,L-3, and Fe L-2,L-3 edges, we find a valence state of Co2+/Rh4+ in Ca3CoRhO6 and of Fe3+/Rh3+ in Ca3FeRhO6. X-ray magnetic circular dichroism spectroscopy at the Co L-2,L-3 edge of Ca3CoRhO6 reveals a giant orbital moment of about 1.7 mu(B), which can be attributed to the occupation of the minority-spin d(0)d(2) orbital state of the high-spin Co2+ (3d(7)) ions in trigonal prismatic coordination. This active role of the spin-orbit coupling explains the strong magnetocrystalline anisotropy and Ising-type magnetism of Ca3CoRhO6.