Zinc-blende CaP, CaAs and CaSb as half-metals: A new route to magnetism in calcium compounds

Existence of ferromagnetism in bulk calcium compounds is discovered theoretically. First-principles calculations of calcium phosphide, calcium arsenide and calcium antimonide in the zinc-blende structure have been performed to show the half-metallic ground state in each optimized stable structure. Magnetism comes from spin-polarization of electrons in $p$-orbitals of P, As or Sb and $d$-orbitals of calcium atoms. The half-metallicity is analogous to the half-metallic zinc-blende compounds, {\it e.g.} CrAs or CrSb, but the predicted compounds become ferromagnetic without transition metals. In (In$_{1-x}$Ca$_x$)Sb, the magnetism remains to be stable in a range of the doping rate ($x>0.8$).