Half-Metallic Ferromagnets and Spin Gapless Semiconductors

A brief review of experimental and theoretical studies of half-metallic ferromagnets (HMF) and spin gapless semiconductors (SGS) is given. The data on resistivity and magnetoresistivity are presented. An important role of non-quasiparticle states owing to electron-magnon scattering in transport properties is discussed. The problem of low-temperature resistivity in HMF is treated in terms of one-magnon and two-magnon scattering processes.