Abstract
We have investigated the electronic structure associated with the ferromagnetic transition of and using high resolution photoemission, Mn 2p resonant photoemission, and O 1s x-ray absorption spectroscopies. The data clearly show that the band gap collapses below the Curie temperature and the density of states at the Fermi level increases with cooling, providing a conclusive microscopic evidence for an insulator-metal transition. Our results suggest that strong small polaron effects, which contribute to a charge fluctuation energy of eV, are responsible for the insulating behavior above which has been enigmatic in the double-exchange model.
- Received 27 July 1995
DOI:https://doi.org/10.1103/PhysRevLett.76.4215
©1996 American Physical Society