Electronic structure of the 2D negative charge-transfer material Sr3FeMO7 (M = Fe,Co).

M. ABBATE; L. MOGNI; F. PRADO; A. CANEIRO

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

The American Physical Society

Año: 2005 vol. 71 p. 195113 - 195113

0163-1829

We studied the relation between the electronic structure and the physical properties of Sr3FeMO7 (M = Fe, Co). The main technique used in the study was Fe 2p, Co 2p, and O 1s X-ray absorption spectroscopy (XAS). The experimental spectra were analyzed in terms of cluster model and band structure calculations. The analysis of the spectra shows that both Sr3FeFeO7 and Sr3FeCoO7 are in the negative-charge transfer regime (this means that their ground states are highly covalent and contain considerable O 2p hole character). The Fe ions are in a high-spin state and the Co ions in an intermediate-spin state stabilized by strong hybridization. The electronic structure helps to explain the trends in the electrical conductivity and the observed magnetic moments. Further, the relatively large O 2p hole weight in the ground state explains also the absence of Jahn-Teller distortions. Sr3FeCoO7 illustrates ferromagnetism and magneto-resistance in a 2D negative charge-transfer material.