Abstract
Removal of oxygen ions by thermogravimetric methods in () produces electron doping of the material and ions are reduced to a trivalent state. Electrical resistivity measurements in samples with controlled oxygen content show a strong increase of the conductivity for samples with . The paramagnetic susceptibility at high temperatures can be described by a Curie-Weiss law with unusually large values for the Curie constant, which is also dependent on the oxygen stoichiometry. These results are interpreted in terms of ferromagnetic - spin clusters formed around the oxygen vacancies. An extension of the Anderson-Hasegawa Hamiltonian for the double-exchange interaction was made in order to understand the electric and magnetic behavior of these materials.
- Received 4 December 1995
DOI:https://doi.org/10.1103/PhysRevB.53.14020
©1996 American Physical Society