Oxygen Annealing Studies of SnO$_{2}$:Co Thin Films Deposited by RF Sputtering

We report on post-deposition oxygen annealing studies of SnO$_{2}$:Co thin films to examine the origin of the room temperature ferromagnetism (RTFM) observed in such materials. Materials are deposited on r-cut sapphire substrates by RF sputtering from a doped target with 5 at.{\%} Co nominal concentration. Magnetization measurements reveal that as-grown samples in Ar atmosphere are non-magnetic at RT. However, by annealing them in low O$_{2}$ pressure (10$^{-4 }$- 2x10$^{-4}$ Torr), the saturation moment increases to $\sim $0.78 $\mu _{B}$/Co at RT, somewhat lower than the expected value for Co$^{2+}$ ions. This verifies that the Co ions are incorporated in the matrix. X-ray diffraction data show a decrease in crystallinity for the most magnetic samples annealed in O$_{2 }$at 2x10$^{-4}$ Torr. To confirm this, further structural and temperature-dependent magnetic measurements for various annealing protocols are underway to determine the nature of magnetism in SnO$_{2}$:Co sputtered thin films.