Junji Numazawa

High sensitivity single-pole head with transverse return-path core of flux

A highly sensitive low noise and narrow-track width, main pole driven type single-pole head has been developed. This head is called TRF head (single-pole head with Transverse Return-path core of Flux flow). It is a kind of main pole driven type single-pole head which operates only on one side of the recording medium[1][2], and is based on a new idea incorporated in the flux return-path portion, to improve the recording and reproducing sensitivity and to reduce its system noise. The TRF head is especially effective for the recording and reproducing with narrow track widths. The development of this head has resolved the problem of insufficient sensitivity in conventional single-pole heads which was a barrier to using narrow track widths, and has provided the prospect of using narrow track width heads necessary for high density digital video recording.

Television home server for integrated services-toward the realization of ISDB "anytime" services

In the age of digital multimedia, demand is bound to rise for a television home server for integrated services which automatically records favorite programs so that users can watch them anytime. We have developed a hierarchical storage management system (HSMS) as the architecture for the development of a high-speed home server with a very large capacity. This paper first describes the required specifications and memory constructions of the home server and then proposes a model of the new HSMS. Also described is its element technologies and an experimental home server system, and the results of the experiment we conducted to test its performance.

Prospect of 1 T bits/in3 video data storage using perpendicular magnetic recording tape

Abstract Future trends for high-density video data storage of 1 T bits/in 3 in multimedia service are discussed in this paper. A magnetic recording tape with CoCrTa/NiFe multilayer has been prepared using a facing targets sputtering system. Read/write characteristics and digital video recording characteristics of this tape have been investigated using a modified conventional VCR. It has been proven that the tape should be highly efficient in high-density recording of 1 T bits/in 3 .

A high‐performance permeance meter and its application to measuring the complex permeability of thin Fe‐Si‐Al‐N films for perpendicular magnetic recording heads

A high‐performance permeance meter has been developed to measure the permeability of thin films for perpendicular magnetic recording heads. The instrument is able to determine small permeance (about 20 μm) with a good signal‐to‐noise ratio in the frequency range of 0.5–120 MHz and, moreover, to reduce the conventional error in the high‐frequency region. The complex permeability of an Fe‐Si‐Al‐N film 200 nm thick for perpendicular magnetic recording heads was measured, and the real part of the permeability was about 3500 with a −1‐dB frequency of about 80 MHz.

Underlayer induced noise and carrier to noise ratio in a double-layer medium

Abstract In this paper we present data on the material properties of the magnetic underlayer of a double-layer medium and how these properties effect the noise during the reproduced process. Using the result of the study, an improved double-layer medium was fabricated. The improvement in the carrier to noise ratio for the oriented underlayer medium was 10 dB when compared to the random orientation of the underlayer on the test sample.

Magnetic force microscopy image of Co–Cr–Ta layer in perpendicular magnetic tape at high linear recording density

In this study, magnetic force microscopy (MFM) was used to investigate the recording capability of a perpendicular magnetic tape at a higher linear recording density. Perpendicular magnetic tapes with polyimide base sheets 10 μm thick were fabricated by a facing-target sputtering system [H. Yoshimoto, K. Kuga, Y. Yoneda, and J. Numazawa, J. Magn. Magn. Mater. 148, 357 (1995)]. A Co–Cr–Ta (200 nm) monolayered tape with a base sheet of excellent surface roughness was fabricated. A complete recorded bit pattern of 250 kfci was observed as a MFM image on the tape. A recorded bit pattern of 300 kfci was also observed. A Co–Cr–Ta/Ni–Fe (150/50 nm) multilayered tape was also fabricated. The remnant magnetization state on this tape at 50 kfci was improved by the presence of an underlayer (Ni–Fe) only 50 nm thick. The MFM image at 250 kfci was the same as with a monolayered tape.

Three-dimensional analysis of the magnetization process of thin-film media

A calculation model in which the medium is considered as a set of many fine magnetic particles is applied to thin‐film media. The magnetic characteristics are calculated for a particle with an initial layer, a particle without an initial layer, and media composed of the particles of either type. The results show that the switching mode of both particles is a quasi‐coherent rotation but the switching field dependence of the particle with an initial layer has curlinglike characteristics. The perpendicular medium with an initial layer is over corrected by 4πMs demagnetization correction.

Magnetic properties and recording characteristics of Co-Cr-Ta-Mo perpendicular recording media

Some Co-Cr-Ta-Mo perpendicular magnetic recording disks with different Mo content (C/sub Mo/) ranging from 13 to 5.1 at.% were fabricated by ion beam sputtering prepared. Magnetic properties, crystal structure and recording characteristics of those media were investigated. The disks with (C/sub Mo/) of 0 to 35 at% exhibited almost the same output values, however the media noise was decreased with increasing (C/sub Mo/). The disks with (C/sub Mo/) of 35 at.% exhibited the highest S/N, of which value 3.2 dB higher S/N, than that of the disks without Mo at a wavelength of 0.34 /spl mu/m.

Preparation of CoCrTa films for high-density magnetic recording tape

Abstract A perpendicular magnetic recording tape for ultrahigh density recording requires a high H c , a high H k and a small Δ H c / H c . Furthermore for use in video tape recorders (VTR), mechanical properties such as reduction in tape curling and optimization of tape stiffness are important. In this study the effect of Ta added to CoCr film and Kr sputtering gas were examined. In addition, CoCrTa thin film media, suitable for VTR tapes, were prepared using a facing targets sputtering (FTS) system.

Analysis of Recorded Track Width Using 3D FEM in Perpendicular Magnetic Recording

Basing on the commercial software JMAG-Studio, we have developed a program in which the magnetization of magnetic particles is introduced into calculations of magnetization distributions in media. This allows us to three-dimensionally analyze perpendicular magnetic recording mechanisms. Even though the media magnetization is introduced into the FEM calculation, the obtained solutions are convergent. In the calculation, the head and media interactions and the demagnetization during the recording process can be accurately considered. Using our program, factors that influence recorded track widths in perpendicular magnetic recording were investigated. Decreasing the magnetic spacing and using a side-shielded head structure are effective ways to reduce the track width in a single-pole head and double layer perpendicular media recording system.