Deposition of single-layer CoFe2O4 and multilayer CoFe2O4/alpha-Fe2O3 with large 4 pi M(s) and high H-c using vacuum arc evaporation

Single-layer CoFe2O4 films with a thickness of 3000 Angstrom were deposited on SiO2/Si wafers at substrate temperatures, T-s, from 50 to 600 degrees C by vacuum are evaporation (VAE) in an oxygen gas atmosphere of about 1 mTorr. Specimen films deposited at a T-s of 400 degrees C were composed of crystallites with clear (311) and (111) orientation and exhibited a 4 pi M(s) of 5.6 kG which was slightly larger than that of bulk perfectly inversed cobalt ferrite. Since the single-layer film possessed almost the same in-plane and perpendicular coercivities of 2.3 kOe, this film may be suitable for isotropic recording media. The multilayer films with 10 X [CoFe2O4/alpha-Fe2O3] bilayers were also deposited under the same conditions. Thicknesses of CoFe2O4 and alpha-Fe2O3 layers were 270 and 30 Angstrom, respectively. The multilayer film deposited at a T-s of 400 degrees C exhibited a 4 pi M(s) of 5.1 kG and the in-plane and perpendicular remanences, 4 pi M(r parallel to) and 4 pi M(r perpendicular to), were 4.7 and 0.55 kG. Moreover, since the in-plane coercivity H-c parallel to of 2.4 kOe was much larger than the perpendicular H-c perpendicular to of 0.35 kOe, these multilayer films seem to be useful for longitudinal recording media.