Experimental and first-principles study on the magnetic and transport properties of Ti-doped Fe3O4 epitaxial films

Structure, magnetic, and transport properties of the epitaxial Fe3-xTixO4 films with x <= 0.09 fabricated by reactive co-sputtering were investigated systematically. The lattice constant expands from 0.8360 to 0.8376 nm with x increases from 0 to 0.09. The room-temperature saturation magnetization increases by 31.7%, and the negative magnetoresistance (at 100 K) increases from 3.7% to 6.9% as x increases from 0 to 0.09. The results indicate that Ti atoms might exist at the tetrahedral sites in the spinel structure. Theoretical calculations based on the density-functional theory suggest that the doped Ti on the tetrahedral sites indeed enhances the lattice constant and magnetic moment. Meanwhile, the calculated results also imply that the Ti-doped Fe3O4 has a high spin polarization near 100%. (C) 2011 American Institute of Physics. [doi:10.1063/1.3650252]