  Scaling relations in the charge and spin excitations of (La,Sr)MnO3 are
studied from both theoretical and experimental points of view. In the
ferromagnetic metal phase, we investigate optical conductivity and neutron
inelastic scattering, and compare with a theoretical calculation based on the
dynamical mean-field theory of the double-exchange hamiltonian. Spin and charge
dynamics of (La,Sr)MnO3 exhibit typical behaviors of half metals. In these
manganite compounds with high Curie temperature, various behaviors in spin and
charge properties are explained by the double-exchange hamiltonian alone.
Magnetoresistance of these compounds as well as other compounds with lower
Curie temperature are also discussed.
