Electronic Structure and Magnetic Properties of New Rare-earth Half-metallic Materials AcFe₂O₄ and ThFe₂O₄: Ab Initio Investigation

Electronic structure and magnetism of the rare-earth metals Ac and Th doped Fe₃O₄ Fe_1-xRe_xFe_2-yRe_yO₄(Re=Ac, Th; x=0, 0.5, 1; y=0, 0.5, 1.0, 1.5, 2.0) are investigated by first-principle calculations. AcFe₂O₄, FeAc₂O₄ and ThFe₂O₄ are found to be II B-type half-metals. The large bonding-antibonding splitting is believed to be the origin of the gap for AcFe₂O₄, FeAc₂O₄ and ThFe₂O₄, resulting in a net magnetic moment of 9.0μ_B, 4.0μ_B and 8.1μ_B, respectively, compared with 4.0μ_B of Fe₃O₄. Also, the conductance of AcFe₂O₄ and ThFe₂O₄ are both slightly larger than that of Fe3O4. It can be predicted that the new rare-earth half-metals AcFe₂O₄ and ThFe₂O₄ have wider application ground in spin electronic devices due to their larger magnetoresistance and higher conductivity than that of Fe₃O₄. The half-metallic feature can be maintained up to the lattice contraction of 8%, 3% and 4% for Fe₃O₄, AcFe₂O₄ and ThFe₂O₄, respectively.