Ferromagnetism in tetrahedrally coordinated compounds of I/II-V elements: Ab initio calculations

On the basis of ab initio calculations employing density functional theory (DFT) we investigate half metallic ferromagnetism in zinc-blende and wurtzite compounds composed of group I/II metals as cations and group V elements as anions. We find that the formation of ferromagentic order requires large cell volumes, high ionicity and a slight hybridization of anion p and cation d states around the Fermi energy. Our calculations show that a ferromagnetic alignment of the spins is energetically always more stable than simple AF arrangements, which makes these materials possible candidates for spin injection in spintronic devices. To clarify the conditions for the flat p-band carrying the magnetism, we present results of a tight binding analysis.