CaB6: A new semiconducting material for spin electronics - art. no. 016401

Ferromagnetism was recently observed at unexpectedly high temperatures in L a-doped CaB6. The starting point of all theoretical proposals to explain th is observation is a semimetallic electronic structure calculated for CaB6 w ithin the local density approximation. Here we report the results of parame ter-free quasiparticle calculations of the single-particle excitation spect rum which show that CaB6 is not a semimetal but a semiconductor with a band gap of 0.8 +/- 0.1 eV. Magnetism in LaxCa1-xB6 occurs just on the metallic side of a Mott transition in the La-induced impurity band.