THEORETICAL-STUDIES ON THE DOUBLE EXCHANGE FERROMAGNET

Based on the double exchange mechanism, a model for ferromagnet La(1-x)M(x)MnO(3) (M=Ca2+, Sr2+, Ba2+, or Pb2+) is developed. Our theory can well describe several Features such as the crossing behaviour of the magnetization curve for different composition x and the steep increase of resistivity around T-c. We use only one free parameter, the e(g)-derived band width W similar to 0.5 eV. The Curie temperature T-c is shown as a function of x.