Perpendicular magnetic anisotropy in 70 nm CoFe_2O_4 thin films fabricated on SiO_2/Si(100) by the sol-gel method

摘要

Cobalt ferrite CoFe_2O_4 films were fabricated on SiO_2/Si(l 00) by the sol-gel method. Films crystallized at/above 600 °C are stoichiometric as expected. With increase of the annealing temperature from 600 °C to 750 °C, the columnar grain size of CoFe_2O_4 film increases from 13 nm to 50 nm, resulting in surface roughness increasing from 0.46 nm to 2.55 nm. Magnetic hysteresis loops in both in-plane and out-of-plane directions, at different annealing temperatures, indicate that the films annealed at 750 °C exhibit obvious perpendicular magnetic anisotropy. Simultaneously, with the annealing temperature increasing from 600 °C to 750 °C, the out of plane coercivity increases from 1 kOe to 2.4 kOe and the corresponding saturation magnetization increases from 200 emu/cm~3 to 283 emu/cm3. In addition, all crystallized films exhibit cluster-like structured magnetic domains.