Jun Ariake

Co-Pt-TiO/sub 2/ composite film for perpendicular magnetic recording medium

A new type of oxide composite film was proposed as perpendicular magnetic recording medium. The storage layer is composed of Co-Pt and Ti-oxide. By transmission electron microscopy (TEM) observation, the film exhibited a well isolated fine granular structure with small and uniform Co-Pt grains surrounded by TiO/sub 2/. More sufficient segregation by TiO/sub 2/ was realized from the beginning of the layer growth compared with other oxide addition film, resulting in a magnetically weak coupled structure. This film has a relatively large magnetic anisotropy constant (K/sub u/) and saturation magnetization (M/sub s/) of more than 5/spl times/10/sup 6/ erg/cm/sup 3/ and about 800 emu/cm/sup 3/, respectively. The structure was brought about by a high sputtering gas pressure of Co-Pt-TiO/sub 2/ film deposition.

Low noise Co-Cr-Nb perpendicular recording media with high squareness

Co-Cr based perpendicular recording media with high perpendicular squareness, SQ/sub /spl perp//, were developed by sputter-deposition, and their noise properties as well as recording performances were studied. It was found that the medium noise strongly correlated to M/sub s//spl middot//spl delta//sup 3/2/(1-SQ/sub /spl perp//)/sup 1/2/, where M/sub s/ and /spl delta/ are saturation magnetization and the thickness of the medium, respectively. Thus a 50 nm thick Co-Cr-Nb medium with a high SQ/sub /spl perp// of 0.74 exhibited the lowest noise among the investigated films. A high S/N of 38 dB for a track width of 2.7 /spl mu/m with a D/sub 50/ of 155 kFRPI was obtained for the Co-Cr-Nb medium by using a MR head. This medium could be used for a recording density of 5 Gbit/in/sup 2/.

Microstructure and magnetic properties of Co/Pd multilayered thin films with C or Si seedlayer

Microstructure and magnetic properties of sputter deposited Co/Pd multilayered perpendicular magnetization films with amorphous C or Si seedlayer were investigated. The angstrom scale surface roughness of the seedlayer causes fine crystal grains to form in the Co/Pd multilayer and to decrease the extent of intergranular exchange coupling, while it obstructs the formation of a regular interface between Co and Pd layers. The Si seedlayer, which exhibits a surface roughness lower than the C seedlayer, yields Co/Pd multilayered films with the lowest intergranular exchange coupling and the highest coercivity. The improvement in magnetic properties of the Co/Pd film with Si seedlayer is attributable mainly to the formation of Pd2Si at the interface between the Co/Pd layer and the Si seedlayer. The Pd2Si provides suitable nucleation sites for the grain growth of Co/Pd multilayered film that can be utilized as a perpendicular magnetic recording medium.

Microstructure and magnetic properties of a Co/Pd multilayer on a controlled Pd/Si seed layer for double-layered perpendicular magnetic recording media

A 10 nm Pd/Si dual thin film was developed as a seed layer for a Co/Pd multilayer in double-layered perpendicular magnetic recording media. The Pd/Si seed layer, sputter deposited under Ar sputtering gas containing N2 and postannealed at 400 °C, markedly reduced intergranular exchange coupling of the Co/Pd multilayered film, resulting in a decrease in both the slope parameter, defined as 4π(dM/dH)H=Hc, and the magnetic cluster size. Consequently, medium noise was essentially reduced, thereby improving the signal-to-noise ratio of the Co/Pd recording media on a CoZrNb soft magnetic underlayer. The addition of N2 gas effectively decreased the grain size of Pd in the seed layer. A Pd/Si seed layer prepared with both processes exhibited a granular structure of fine Pd-rich grains surrounded by a Si-rich amorphous region, which provided nucleation sites for the growth of well-separated Co/Pd multilayered grains.

Preparation of double-layered perpendicular media for fine magnetic structure

Two preparation methods for sputter deposition are examined in order to obtain a low noise double-layered layered perpendicular recording medium. Very thin intermediate layers between the recording layer and the soft magnetic backlayer was found to reduce the medium noise. Nitrogen addition to the NiFe system backlayer was also effective in reducing the noise. The medium noise reduction was attributed to the reduction in grain size and a magnetic domain size of the recording layer in both cases. An MFM image corresponding to a density beyond 50 Gbit/in/sup 2/ was observed for a medium with Co-Zr-Nb intermediate layer.

Nb addition to CoCr media for perpendicular magnetic recording

Abstract Nb element has been investigated as an additive metal for a CoCr alloy thin film. It was found that Nb addition has almost the same effects as conventional Ta addition with regard to the resulting magnetic properties when substrates of the same quality are used. For the new CoCrNb medium, a high recording density of up to 720 kFRPI can be achieved. It is indicated that the recording resolution of the CoCrNb medium is at least as high as that of a conventional CoCrTa medium.

High coercivity in Co-Cr films for perpendicular recording prepared by low temperature sputter-deposition

Hc/sub /spl perp// over 1000 Oe has been achieved for Co-Cr films deposited at room temperature and at an extremely high Ar pressure onto a Ti underlayer. Conditions for further high Hc/sub /spl perp// were studied. After optimization of the Ti underlayer thickness, an Hc/spl perp/ of 1370 Oe was obtained for Co-Cr films of 45 nm thick, in which a high c-axis orientation could be sustained by hetero-epitaxial growth. Magnetic isolation of columns was realized by a voided structure by shadowing effect at high deposition pressures and oxide formation. The high Hc/sub /spl perp// is determined by large perpendicular anisotropy, grain size and the magnetic isolation of columns, but the isolation manner very differs from the micro-segregation of Cr in conventional high Hc films deposited at high temperatures and low pressures,. >

Addition of third elements to CoCr media

Abstract The effects of the third-additive metals (Nb, Ta, Zr and Pt) on magnetic properties of CoCr alloy thin-film media have been extensively studied. It was found that perpendicular coercivities ( H c⊥ ) decreased monotonically with increasing Zr addition, while the H c⊥ increased and exhibited a maximum value with the addition of 3–4 at% of Nb or Ta and about 12 at% of Pt. Further addition of Pt seemed to decrease the degree of magnetic isolation between particles. Nb addition brought a higher saturation magnetization ( M s ) at the maximum value of H c⊥ than that of Ta addition. The effects of simultaneous addition of Nb, Ta and Zr are also described.

Write Margin Improvement in Bit Patterned Media With Inclined Anisotropy at High Areal Densities

Bit patterned media with inclined anisotropy were proposed along with media design with a higher saturation magnetization and a small thickness for the dot. Inclination of the anisotropy axis was found to reduce broadened switching field distribution of the media caused by the magnetostatic interaction between the dots. Recording simulation at an areal density of 2.6 Tbit/in2 using a write field of a shielded planar head exhibited substantially increased write shift margins of 6.5 nm and 10 nm in down- and cross track directions, respectively, for the media with inclined anisotropy when the anisotropy dispersion of the media was as small as 2%. Recording density was expected to be increased beyond 4 Tbit/in2 for the media with additional exchange coupling between the dots.

Fabrication of SmCo Double-Layered Perpendicular Magnetic Recording Media

We fabricated SmCo5 double-layered perpendicular magnetic recording media with high perpendicular magnetic anisotropy for realizing ultra high density recording. A double-layered medium with a Ru buffer layer introduced between a Cu/Ti intermediate layer and a Co-Zr-Nb soft magnetic underlayer exhibited high perpendicular magnetic anisotropy, whereas that without the Ru buffer layer did not. Auger electron spectroscopy revealed that the Ru buffer layer inhibited interdiffusion between the Cu/Ti intermediate layer and the Co-Zr-Nb soft magnetic underlayer. We report here for the first time the read-write characteristics of SmCo5 double-layered perpendicular magnetic recording media. The medium noise was small in the medium with a Sm-Co layer deposited under high Ar gas pressure owing to small magnetic clusters