Magnetic anisotropy and high coercivity of epitaxial Co-ferrite films prepared by pulsed laser deposition

Co Fe2 O4 films with different thicknesses (40-200 nm) were prepared on sapphire using pulsed laser deposition at different substrate temperatures. The films on (0001) sapphire showed a (111) epitaxial structure even at a low deposition temperature of 150 °C. The coercivity up to 8.8 kOe could be achieved in the 40 nm film on sapphire deposited at 550 °C. By comparison, the 33 nm film on quartz possesses a nanocrystalline structure with the grain size below 20 nm as well as a strong (111) preferential texture. The highest coercivity (12.5 kOe) up to now was obtained in the 33 nm Co-ferrite films. The study also revealed that high coercivity and large perpendicular anisotropy of these Co-ferrite thin films may be related to the textured structure and large residual strain.