New Theoretical Characterizations for Half-Metallic Ferromagnets

In the current literature Half-Metallic Ferromagnets (HMFs) have been theoretically characterized mainly by using the Band Theory approach. As a matter of fact, a first standard characterization of HMFs states that a HMF is a ferromagnet in which spin-up electrons have metallic band structure whereas spin-down electrons have insulating or semiconducting band structure. A second standard characterization says that a HMF is a ferromagnet in which at T=0K the density of states for the spin-down component at the Fermi level is zero whereas the density of states for the spin-up component at the Fermi level is different from zero. In this work, we propose new ways of theoretically characterizing HMFs by using an approach based on Fermi Liquid Theory for Spin Polarized Systems and the concept of exchange splitting, These new characterizations have proved to be useful in describing the thermodynamics and spin dynamics of HMFs in a way consistent with experiment.