Colossal magnetoresistance of half-metallic ferromagnets with low carrier-densities

Abstract The magnetic resistivity ρ is restudied theoretically for ferromagnetic metals, which are assumed to have spins localized at magnetic ions and carriers of low density. It is shown that the half-metallic state realized under nonzero magnetizations exhibits low ρ 's, while ρ is extraordinary enhanced near T c because of the smallness of the Fermi surface. The obtained ρ gives the characteristics of the colossal magnetoresistance observed.