Ryuji Sugita

Magnetic and microstructural studies of CoCr films

Abstract This paper contains a review of magnetic properties, microstructure and segregated microstructure of Coue5f8Cr films. One of the most distinctive features of the Coue5f8Cr films is segregated microstructure, which results in the increase of coercivity HC⊥ and of the ratio of the rotational reversal mechanism to the wall displacement. For the Coue5f8Cr films deposited with oblique incident atoms, the direction of the easy axis is in between the growth direction of the columns and the c axis.

Method for providing a perpendicular recording medium for use with a ring-shaped recording and reproducing head

A perpendicular magnetic recording method uses a perpendicular magnetic recording medium. This medium comprises a perpendicular anisotropy film having perpendicular remanent magnetization Mr and longitudinal remanent magnetization Mr.sub.∥, wherein the value of the ratio Mr.sub.⊥ /Mr.sub.∥ is not less than 0.2, but is less than 1.

Incident angle dependence of the magnetic properties of vacuum deposited Co-Cr films

Abstract The incident angle and the substrate temperature dependence of the magnetic properties of continuously vacuum deposited Co-Cr films was investigated. The inclination of the easy axis form the film normal toward the film plane in the incidence plane became large with increasing incident angle. The magnetic anisotropy field of the films deposited at oblique incidence decreased with increasing substrate temperature. X-ray analysis and TEM observation showed that the magnetocrystalline anisotropy was dominant at low incident angle and the shape magnetic anisotropy was dominant at high incident angle. Also investigated was the effect of an initial layer on the magnetic properties and the crystal orientation of a Co-Cr film. The easy axis of the film was titled by the Co-Cr initial layer deposited at high incident angle, because the c -axis tilted as a cinsequence of epitaxial growth on the initial layer.

Improvement of Performance in Continuously Vacuum Deposited Co-Cr Film by Substrate Treatment

Dependence of the perpendicular anisotropy of continuously vacuum deposited Co-Cr films on glow discharge treatment of the polymer base film surface, and on the thickness of a Ti underlayer, was investigated. The relation between the film microstructure and the recording characteristics of the Co-Cr film media was also studied. When the polymer film surface was pretreated by glow discharge with Ar gas, the Hkeff of the Co-Cr films decreased, but when H2 gas was used instead of argon, the deterioration of the Hkeff was negligible. Co-Cr films deposited on a Ti underlayer had a high Hkeff regardless of the glow discharge treatment conditions. The Ti underlayers had to be more than 40 Å thick in order for the Co-Cr films to have a small ¿¿50, around 5 or 6°. The Co-Cr films showed a columnar structure when the Ti underlayer thickness was in the range from 100 to 2000 Å Co-Cr films with a columnar structure yielded a high reproduced voltage.

Co-Cr Perpendicular Anisotropy Film Deposited by Evaporation with Ion Bombardment

The effect of ion bombardment during film growth was investigated for perpendicular anisotropy CoCr films. Films were prepared by a web-coater type evaporating system equipped with a Kaufman 3-cm ion source. The M_s, H_{c ⊥} and δθ₅₀ decreased, while H_{k/spl pert/} and the grain size increased, in bombarded films. These results indicate a reduction in crystallographic defects and Cr segregation, suggesting that grain boundaries play an important role in the segregation.

Perpendicular magnetic recording tapes suitable for ring heads

Abstract The application of perpendicular magnetic recording technology is requisite in order to realize a next generation digital VCR whose recording density is about 1 bit/μm2. Since ring heads will be used for the digital VCR, tapes must be suitable for the ring heads and digital signals. Tape with a titled easy axis is one of the candidates, which has single-peak-like isolated reproduced waveform, the spacing loss factor lower than that of the tape with a non-titled easy axis, and high reproduce voltage not only at high linear densities but at low densities.

Co-Cr Thin Films Deposited on Substrates with Island Structure

The effect of substrate morphology on the perpendicular anisotropy of Co-Cr films was studied. Co-Cr layers were deposited on top of Al-3 wt% Cu underlayers; the latter were of thickness 1.5 to 40 nm and were deposited at a substrate temperature of from 25 to 300°C. SEM photographs revealed an island structure for the Al-Cu films deposited at 300°C, while those deposited at 25°C had a flat surface. The ¿ ¿50 and Hkeff of Co-Cr films on Al-Cu underlayers deposited at 300°C were about 15° and 2 kOe respectively, while the figures when the Al-Cu layer was deposited at 25°C were under 10° and about 3 kOe respectively. The morphology of the Al-Cu underlayer thus greatly influenced the perpendicular anisotropy of the Co-Cr film.

Substrate Temperature Effect on Magnetic Properties and Microstructure of Vacuum Deposited Co-Cr Films

The authors investigated the effect of substrate temperature and substrate thickness on the magnetic properties and microstructure of vacuum-deposited Co-Cr films. The microstructure of films is sufficiently dependent on the substrate temperature that the columnar structure disappears as the temperature rises from 250°C to 290°C, causing deterioration of the film recording characteristics. The substrate thickness dependence of the film magnetic properties is small; this result is consistent with simulations of the thickness dependence of the substrate temperature during deposition.

Effect of Ni Addition on Magnetic and Recording Properties of Continuously Vacuum-Deposited Co-Cr Films

We investigated the effect of the addition of Ni to continuously vacuum deposited Co-Cr films on magnetic characteristics, crystal structure, microstructure and reproduced voltage. The following results were obtained. (1) The addition of 40 wt% or less Ni had the effect of increasing the perpendicular Hc. In Co-Cr-Ni films which contain approximately 20 wt% Ni, the highest perpendicular Hc was obtained. In other words, it is possible to lower the temperature by approximately 50°C with adding 20 wt% Ni. (3) With increase in Ni content, the Hkeff decreases monotonically and the fcc phase increases. The films which contain 30 wt% Ni achieve high reproduced voltage in spite of the substantial intermixing of the fcc phase. Consequently, films with the perfect hep structure are not necessary in order to achieve high reproduced voltage.

Recording and Reproducing Characteristics of Vacuum-Deposited Double-Layer Perpendicular Recording Disks

This paper reports on research into the recording and reproducing characteristics of vacuum deposited CoCr/NiFeCo double-layer perpendicular recording media. It was found that when NiFeCo film was used as the underlayer, reproducing output of the media was improved and was isotropic in plane.