  We introduce a two-band Kondo-lattice model to describe ferromagnetic
half-metals with local magnetic moments. In a model study, the electronic and
magnetic properties are presented by temperature dependent magnetization
curves, band-structures, spin polarizations and plasma frequencies. These are
obtained from numerically evaluated equations, based on the single-electron
Green functions. We show that the mutual influence between the itinerant
electrons and the local magnetic moments is responsible for several phase
transitions of the half-metals, namely first and second order magnetic phase
transitions, as well as half-metal to semiconductor and half-metal to semimetal
transitions.
