Emergence of half-metallicity in suspended NiO chains

Contrary to the antiferromagnetic and insulating character of bulk NiO, one-dimensional chains of this material can become half-metallic due to the lower coordination of their atoms. Here we present ab initio electronic structure and quantum transport calculations of ideal infinitely long NiO chains and of more realistic short ones suspended between Ni electrodes. While infinite chains are insulating, short suspended chains are half-metallic minority-spin conductors which display very large magnetoresistance and a spin-valve behaviour controlled by a single atom.