Abstract
Using and x-ray absorption spectroscopy, we reveal that the charge ordering in involves high spin () and low spin () ions. This provides evidence for the spin-blockade phenomenon as a source for the extremely insulating nature of the series. The associated and orbital occupation accounts for the large contrast in the Co-O bond lengths and, in turn, the high charge ordering temperature. Yet, the low magnetic ordering temperature is naturally explained by the presence of the nonmagnetic () ions. From the identification of the bands we infer that is a narrow band material.
- Received 26 November 2008
DOI:https://doi.org/10.1103/PhysRevLett.102.116401
©2009 American Physical Society