A possible path to a new class of ferromagnetic and half metallic   ferromagnetic materials
  We introduce a path to a possibly new class of magnetic materials whose properties are determined entirely by the presence of a low concentration of specific point defects in their crystal structure. Using model Hamiltonian and ab-initio band structure methods we demonstrate that even large band gap nonmagnetic materials as simple as CaO can exhibit extraordinary properties like half metallic ferromagnetism upon introducing a small concentration of Ca vacancies. We show that such defects will initially bind the introduced charge carriers at neighboring sites and depending on the internal symmetry of the clusters formed by neighboring sites form "local" magnetic moments which for concentrations as low as 3% transform this non-magnetic insulator into a half metallic ferromagnet. 
I.S. Elfimov, S. Yunoki, and G.A. Sawatzky