Double-exchange interaction in electron-doped CaMnO32d perovskites

J. BRIÁTICO; B. ALASCIO; R. ALLUB; A. BUTERA; A. CANEIRO; M.T. CAUSA; M. TOVAR

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Lugar: New York; Año: 1996 vol. 53 p. 14020 - 14023

1098-0121

Removal of oxygen ions by thermogravimetric methods in CaMnO32d (0<d<0.34) produces electrondoping of the material and Mn41 ions are reduced to a trivalent state. Electrical resistivity measurements insamples with controlled oxygen content show a strong increase of the conductivity for samples with(32d )52.75 and 2.84. 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 Mn31-Mn41 spin clusters formed around theoxygen vacancies. An extension of the Anderson-Hasegawa Hamiltonian for the double-exchange interactionwas made in order to understand the electric and magnetic behavior of these materials.