  A version of the magnetoimpurity theory of the colossal magnetoresistance
materials suitable for the double exchange ferromagnetic nondegenerate
semiconductors is presented. It provides an explanation of the nonmonotonic
temperature dependence for the charge carrier density in them when it displays
first a maximum and then a minimum, on increase in temperature. Respectively,
the resistivity displays first a minimum and then a maximum. The theory is
based on the relation between the charge carrier activation energy and the
change in the magnon free energy caused by the ionization of an impurity. This
is tantamount to the relation between the charge carrier density and the so
called giant red shift of the optical absorption edge.

Strongly Correlated Electrons;Materials Science