Sputtered Fe-Hf-C-N films were investigated to examine the effect of simultaneous addition of C and N elements on the magnetic and structural properties. The as-deposited films having phases of amorphous and bcc a-Fe or near fully crystalline a-Fe phase showed excellent soft magnetic properties upon annealing, reaching the permeability (μ_<eff> at 1 MHz ) of 8200. The thermal stability of the Fe-Hf-C-N films was also found to be excellent; e.g., H_c was less than 0.3 Oe and μ_<eff> was about 4000 for the films annealed up to 700℃. The films exhibited high μ_<eff> of more than 6000 and 4πM_s of about 17 kG in the composition range where the Hf content is about 7 at% and the ratio of [C+N]/[Hf] is around 1.5. The fine grained a-Fe structure, together with finely dispersed Hf(C,N) precipitates which formed at an early stage of crystallization is considered to be one of the main factors for the excellent magnetic properties and thermal stability.
Co/Cu artificial superlattices were fabricated with a three-gun RF magnetron sputtering system. Effects of copper underlayer thickness and cobalt layer thickness on the magnetoresistance curve were investigated It has been found that the crystallinity of the multilayered film is closely related to the thicknesses of the cobalt layer and the copper underlayer. In the [Cu(20Å)/Co(30Å)]_<20>Cu-6at%(200Å)|Si sample which showed the magnetoresistance of 20.6% at room temperature less than 200 Oe as the saturation field could be obtained. Relationship between crystallinity and the saturation field is discussed.
Effects of process parameters on the magnetic and recording characteristics of magneto-optical disk were investigated Magneto-optical media having four layered structure were fabricated under varying sputtering conditions such as sputtering pressure, power. target-to-substrate spacing and incident angle of deposition. Magnetic coercivity was sensitively affected by pressure, power and Larger-to-substrate spacing, since the change in scattering of sputtered atoms at different pressure or power induce a slight change in terbium content. The domain wall transition behavior was strongly influenced by pressure as well. The magneto-optical disk consisting of dense TbFeCoCr layer exhibited a high write bias field sensitivity due to the fast domain wall motion and uniform switching field. As the incident angle of arriving particles increased, despite the excellent perpendicular anisotropy, the nucleation of reverse domains near coercivity became non-uniform. Microstructure of TbFeCoCr layer varying with deposition parameters appeared to play an important role in determining the magnetic and recording characteristics of magneto-optical disk.
Computer simulations for thin films of amorphous rare earth-transition metal alloys which are used for magneto-optical recording media are performed. In these simulations, the recording media are two dimensional lattice of 64×64 magnetic moments with lattice distance 10Å. The motion of the magnetic moments follows the dynamic equation of Landau-Lifshitz-Gilbert(LLG) under the influence of an effective field arising from the local anisotropy, nearest-neighbor exchange, classical dipole-dipole interaction, and an external applied field. According to the LLG equation, we have investigated the process of domain wall formation for a medium with random axis anisotropy δ_θ. For nonzero of δ_θ, it was found that 2π-Bloch wall line appear at the boundaries of magnetic domain and it is jagged. Finally, the effects of exchange stiffness coefficient A_x and anisotropy coefficient K_u on the wall width and the dispersion which represcnts jaggedness of domain wall are studied.