Effect of Cu doping on room temperature ferromagnetic behavior of Mn doped LiNbO3 films.

Cu and Mn co-doped LiNbO 3 films were deposited on Si (111) substrates by rf-magnetron sputtering. XRD shows a randomly oriented polycrystalline R3C structure of LiNbO 3 was formed in the films annealed at 1000 °C for 1 h in air. XPS and XAFS determine that Mn 2+ substitutes on the Li site with a Li vacancy and Cu 2+ substitutes on the Nb site with an oxygen vacancy in the LiNbO 3 lattice. SQUID measurements indicate that all the films exhibit room temperature ferromagnetism, attributed to a strong d–d electron interaction between Mn and Nb and the bound magnetic polarons resulting from the oxygen vacancies. The saturated magnetization increases but the atom magnetic moment decreases with increasing Cu content in the films. The drop of the atom magnetic moment may arise from the antiferromagnetic coupling among adjacent Cu ions and an antiparallel configuration between Cu 2+ ions and their trapped electrons. [ABSTRACT FROM AUTHOR]