Koichi Osano

Multilayered films of nitride alloys as magnetic head materials

Abstract Multilayered alloy films composed of non-nitride and nitride layers were prepared by N 2 reactive sputtering. Soft magnetic properties were obtained for the films comprising metal-metal elements such as Co-Nb-Zr/Co-Nb-Zr-N when the layer thickness is less than 30 nm and for the films comprising metal-metalloid elements such as Fe-Nb-B/Fe-Nb-B-N when it is less than 60nm. The films showed high 4π M s (12–17kG) and a high permeability (2000–4000 at 1 MHz) after magnetic field annealing at 400–700°C. Magnetic VCR heads manufactured with Co-based multilayered films showed extremely high efficiency both in recording and reproducing characteristics.

Effect of Residual Stress on the Recording Characteristics of a Magnetic Head.

We propose a system for analyzing the magnetic field of a magnetic head, taking account of the residual stress distribution. This simulation system is composed of three analytic parts: a thermal stress distribution analysis part, a permeability distribution analysis part and a magnetic field analysis part. The system was applied to ametal-in-gap-type magnetic head in order to investigate the effect of residual stress on the recording characteristics. We assumed that the stress was caused by the difference in the thermal expansion coefficients of the constituent materials. The permeability reaches a maximum for an optimum combination of thermal expansion coefficients, which are different for ferrite, thin magnetic metal film and bonding glass. The calculated output agrees well with the measured output. Use of the system optimizes the magnetic head in terms of the residual stress.

Magnetic Properties of Co-Based Multi-Layered Nitride Films

To improve the magnetic properties of Co-based multilayer nitride films, we investigated the conditions of film preparation, including the composition, N<inf>2</inf> partial pressure, total gas pressure, annealing temperature and gas-flow rate. The results were the following. The B<inf>s</inf> increased with Co content, at the rate of about 1 kG per 3 to 4 at% Co, but did not depend on the annealing temperature at temperatures above 515C. ¿<inf>s</inf> decreased with increasing Co content, and increased with increasing annealing temperature. Neither ¿<inf>s</inf>, H<inf>c</inf>, or B<inf>s</inf> depended on the total gas pressure or gas-flow rate. Near a Co content of 86 at%, ¿<inf>s</inf> was less than ±1×10^¿6 and B<inf>s</inf> was about 13 kG.

Laminated Head for VTR with Co-Based Super-Structured Nitride Alloy Films

The recording characteristics and wide-band playback characteristics of laminated heads composed of Co-base superstructured nitride alloy films were investigated. The superstructured alloy film was composed of 250 Å thick nonnitride and nitride layers of Co-Nb-Zr, and had higher thermal stability, higher saturation flux density, and higher initial permeability at high frequencies than does conventional Co-Nb-Ta-Zr amorphous alloy film. Because of these excellent properties, excellent recording performance and wide-band playback characteristics were achieved for laminated heads with narrow gap lengths.

Magnetic properties of Fe based compositionally modulated nitride alloy films

In the Co-metal based compositionally modulated nitride alloy films, we have noted the fact that the affinity in regards to nitrogen differs among metal elements such as Co and Nb. We have examined systems which contain the metallic elements (Nb) and metalloid elements (B) which have a strong affinity towards nitrogen as Fe-based compositionally modulated nitride alloy films. Based on this, the compositionally modulated nitride alloy films in the Fe-Nb alloys and the Fe-Nb-Si-B alloys show high saturation magnetization and good soft magnetic properties after high temperature annealing. Thus, their suitability as soft magnetic alloy films for use with magnetic heads has become clear. Herein, we report on Fe-based compositionally modulated nitride alloy films. Using the reactive sputtering method, Fe-based compositionally modulated nitride alloy film (CMNF) was formed.