Electronic structure and magneto-optic Kerr effect in ferromagnetic titanium oxyphosphates Li0.50Co0.25TiO(PO4): An ab-initio study

The X-ray diffraction for Li0.50Co0.25TiO(PO4), was used as a starting point to perform structural optimization by minimizing the forces acting on the atoms. We have performed a comprehensive theoretical study of electronic properties, including magneto-optic Kerr effect, of titanium oxyphosphates Li0.50Co0.25TiO(PO4) in the ferromagnetic phase. The generalized gradient approximation (GGA) exchange-correlation potential was applied within the full potential linear augmented plane wave (FP-LAPW) method. The total energy of the ferromagnetic state is 0.72 eV less than that of the paramagnetic state. The total moment is found to be 2.99 mu(B) with a major contribution of 2.47 mu(B) coming from the Co atoms. In addition, we have calculated the total and partial densities of states. The electron charge densities and the bonding properties are analyzed and discussed. As a remarkable finding we note that the ferromagnetic Li0.50Co0.25TiO(PO4), is semiconducting with energy gap of about 1.2 eV for the minority spin and as semi-metallic for the majority spin, in contrast to the paramagnetic Li0.50Co0.25TiO(PO4) which shows metallic behavior. From the calculated results of band structure and density of states, the half-metallic character and stability of ferromagnetic state for Li0.50Co0.25TiO(PO4) is determined. The bonding properties of the ferromagnatic Li0.50Co0.25TiO(PO4) have been analyzed through the electronic spin charge density contours in the (1 0 0) and (1 1 0) planes. The Kerr rotation spectrum is controlled by sigma(xy)(2) (omega) at low energies (1.5-3.0 eV) because sigma(xx)(1) (omega) is almost constant. The value of the Kerr rotation is close to 0.1 degree at low energies. (C) 2012 Elsevier B. V. All rights reserved.