Theoretical Study of Magnetism in Transition Metal Doped TiO2 and TiO2-delta. }

L. A. ERRICO, M. RENTERÍA, AND M. WEISSMANN

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

The American Physical Society

Lugar: New York; Año: 2005 vol. 72 p. 184425 - 184425

0163-1829

La referencia correcta es: phys. Rev. B 72, 184425-1, siendo la última página 184425-8 (8 páginas). El sistema no permite ingresar caracteres alfanuméricos In recent years there has been an intense search for roomtemperature ferromagnetism in semiconductors doped with dilute magnetic impurities (DMS), in particular, oxides. In this work we study the structural, electronic, and magnetic properties of doped rutile TiO$_2$ for two different impurity concentrations (25$%$ and 6.25$%$), considering different distributions of the impurities in the host lattice. Calculations were performed with {it ab initio} methods, assuming that the magnetic impurities substitutionally replace the Ti ions. Our results show that a local magnetic moment appears in the cases of  Mn, Fe, and Co impurities, but not in the case of Ni and Cu impurities. They also show that in the system Ti$_{1-x}$Co$_x$O$_2$ the magnetic ions align ferromagnetically, while in Ti$_{1-x}$Mn$_x$O$_2$ and Ti$_{1-x}$Fe$_x$O$_2$ the antiferromagnetic alignment is energetically favorable. We have also studied the effect of oxygen vacancies, which turnedout to be very important. Their presence decreases the energyrequired to introduce the impurities in the host lattice andreciprocally, the presence of impurities is related to a highervacancy concentration. The pairs impurity-nearest neighbor oxygenvacancy seem to be the energetically preferred structures and toproduce the highest local magnetic moments.  Ni and even Cuimpurities acquire magnetic moments in this environment.