Co-Zn Ferrite Films Research Articles

Magnetic Properties of Nanocrystalline Co0.9Zn0.1Fe2O4

Nanocrystalline Co-Zn ferrite films grown on thermally oxidized silicon wafers were fabricated by a sol-gel method. Magnetic and structural properties of the films were investigated using X-ray diffraction, atomic force microscopy (AFM), scanning electron microscopy, Auger electron spectroscopy, and vibrating sample magnetometer (VSM). Ferrite films annealed above 673 K had only a spinel structure without any preferred crystalline orientation. In polycrystalline thin films, their composition was confirmed to be Co:Zn:Fe:O = 0.9:0.1:2.0:4.0 and there was no observation of inter-diffusion between the ferrite film and the substrate. Images of AFM show that their rms surface roughness was less than 5 nm and that the size of grains was about 48 nm for annealing temperatures greater than 1073 K. The results of VSM measurement show that the films had a moderate saturation magnetization and that there was no significant difference of their magnetic properties while applying an external field parallel and perpendicular to planes of the films. The maximum value of the coercivity was 1900 Oe for Co-Zn ferrite thin film annealed at 873 K.

磁性材料の化学 スパッタ法・めっき法によるフェライト薄膜の堆積技術と構造・物性の比較

The present paper describes synthesis techniques of ferrite thin films by the facing-targets sputtering and the ferrite-plating methods. The difference in microstructure, crystallinity and magnetic properties of the ferrite films deposited by the two deposition methods is caused by the difference in energy which atoms and ions have in order to migrate on and around substrates. Co-M ferrite films (M=Zn, Ni) deposited by the two methods for magnetic recording media were investigated. Since the sputtered atoms have higher migration energy than the plating ions, the sputter-deposited Co-Zn ferrite films exhibited closely packed finer microstructure, better crystallinity, and higher mechanical strength. Co-Ni ferrite-plated films had excellent perpendicular magnetic anisotropy though the microstructure must be improved to apply to the magnetic recording media. The ferrite plating has the advantages in coating micrometersize particles used as magnetically separable carriers such as for medical applications because it is a wet process.

Preparation and characteristics of Co-Zn ferrite rigid disks without protective layers for high density recording

Spinel type of Co-Zn ferrite films were deposited on glass ceramic disk substrates of 1.89 inch diameter by using a facing targets sputtering apparatus without post-annealing process. Films deposited at substrate temperature T/sub s/ of 200 and 400/spl deg/C were composed of crystallites with clear (111) and (311) orientation, respectively. Disks with (111) orientation (Disk(111)) possessed larger perpendicular component of magnetization than that with (311) orientation (Disk(311)). The center-line average roughness R/sub s/ of Disk(111) and Disk(311) were 1.1 and 4.0 nm, respectively. Their read/write characteristics were examined without protective layer by using a merged type of magnetoresistive (MR) head with shield gap length of 0.27 /spl mu/m. The linear recording density D/sub 50/ increased with decrease of the thickness of recording layer for both disks and the highest D/sub 50/ was 1.36 kfrpi for Disk(111) 50 nm thick and 86 kfrpi for Disk(311) 35 nm thick, respectively.

Sputter Deposition of Ferrite Films and Application for High Density Rigid Disk Media in Contact Mode

Co-Zn ferrite and BaM ferrite films were deposited on silicon wafer disks with thermally oxidized surface layer without annealing process, and their read/write characteristics in contact mode have been investigated by using a MIG and Mn-Zn ferrite head with gap length of 0.2-0.4 μm. The highest linear recording density D 50 of Co-Zn ferrite and Ba ferrite films were 105 and 190 kFRPI, respectively. Clear dipulse was observed for isolated wave form of Ba ferrite disks and then dipulse ratio was 0.65. It was concluded that the Co-Zn ferrite films and Ba ferrite films have high potential as an isotropic and a perpendicular recording layer, respectively, in contact recording mode at ultra-high density.

Preparation of Ferrite Rigid Disks with Isotropy and Read/Write Characteristics

Co-Zn ferrite films were deposited using the facing targets sputtering apparatus and their read/write characteristics were investigated as well as crystallographic and magnetic ones. Co-Zn ferrite films deposited at substrate temperature Ts of 100 and 400 °C revealed very smooth surface and the minimum center-line average roughness Ra were 2.5 and 3.0 nm, respectively. They were composed of crystallites with (111) and (311) orientation and possessed an isotropy and in-plane magnetic anisotropy. High linear recording density of about 114 kFRPI was achieved for specimen disks with (111) orientation which were deposited on fused quartz disk substrate using MIG type head with gap length of 0.27 μm.

磁性材料の化学 プラズマフリー・スパッタ法で作製したＣｏ‐Ｚｎフェライト膜の結晶性と磁気特性

Co-Zn ferrite films were expected for high density magnetic recording media and magnetic thin film devices because of its large magnetocrystalline anisotropy energy and high coercivity. Facing Targets Sputtering (FTS) method was used to deposit Co-Zn ferrite films and the films composed of well (111) oriented crystallites were attained at the substrate temperature T2 below 100°C by using sintered targets with the composition of Co0.51Zn0.45Fe2.04Oy The maximum value of saturation magnetization 4πMs of 4.8 kG was attained at Ts of 250°C and the in-plane and perpendicular coercivities, Hc// and Hc⊥ were around 1.8 kOe, respectively. It was also found that the preferred orientation of Co-Zn ferrite crystallites were strongly dependent on Ts.

Read/write characteristics of Co-Zn ferrite rigid disks in contact mode recording

Co-Zn ferrite films were deposited at substrate temperature T/sub s/ from 90 to 500/spl deg/C by using facing targets sputtering. Specimen films deposited at T/sub s/ of 200/spl deg/C and below were composed of crystallites with excellent (111) orientation and possessed a very flat surface, where the center-line average roughness R/sub a/ was 2.5 nm. The saturation magnetization 4/spl pi/M/sub s/ took a maximum value of 4.8 kG at T/sub s/ of 250/spl deg/C and the in-plane and perpendicular coercivities H/sub c/spl par// and H/sub c/spl perp// were both 1.5 kOe. A high linear recording density of 105 kFRPI was achieved for a specimen disk with Co-Zn ferrite film deposited at 200/spl deg/C by using a MIG type head with gap length of 0.27 /spl mu/m.

Co-Zn ferrite rigid disks prepared by plasma-free sputtering at low substrate temperature

Co-Zn ferrite films deposited at substate temperature T/sub c/ below 200/spl deg/C and above 400/spl deg/C by using facing targets sputtering apparatus are composed of crystallites with (111) and (311) orientation, respectively. A maximum 4/spl pi/M/sub s/ of 4.8 kG was obtained at T/sub s/ of 250/spl deg/C and then H/sub c/ was about 1.5 kOe. The linear recording density of 31 kFRPL was obtained and it is the highest value to be reported for ferrite disk media compared to previous studies using a ring type head.