Hiroaki Wakamatsu

Noise characteristics of CoCrTa/NiFe perpendicular recording media

The authors show that the spike-noise peak frequency is from 20 to 40 kHz at a velocity of 13 m/s. This frequency does fall wide of the frequency band of data, so it can be removed by a high pass filter. It is also shown that storage-layer noise is the greater part of the total medium noise. The low noise medium was used with a narrow pole contact recording head. A total signal-to-noise ratio of over 20 dB at a recording density of 1 Gb/in/sup 2/ (17 kTPI, 60 kBPI) was obtained. >

High-energy Co-Cr thin films sputtered on glass disks for perpendicular recording

The authors have developed high-energy Co-Cr thin-film perpendicular recording media for rigid disks. They obtained high perpendicular coercivity (Hc perpendicular to ) exceeding 2000 Oe with Co-Cr films sputtered on glass disks. They examined recording characteristics obtained with double-layered media and single-pole heads. Readout voltages were proportional to Hc perpendicular to up to 2000 Oe and not dependent on saturation magnetization. The authors explain the experimental results using the hysteresis curve of the Co-Cr film and the permeance factor determined by the magnetic reluctance of the head and medium. Using a magnetic circuit model, they clarify the effect of the difference in the operating point on the hysteresis curves of rigid- and flexible-disk systems. >

High SNR perpendicular recording media

Abstract We investigated the effect of a Ti interlayer in perpendicular double-layer disks to give a typical columnar structure and a good crystal orientation. Coercivity in thinner Co-Cr with Ti is larger than that without Ti. However, we found the Ti layer was not good for high density recording because of its spacing loss. The effects of Ta in a Co-Cr layer on coercivity are also studied particularly in thin film. The effect of Ta is similar to that of a Ti interlayer in coercivity but very superior in recording characteristics. We also measured signal-to-noise ratio at very high density and got 16 dB of SNR at a density of 2 Gbit/in 2 using the Co-Cr-Ta film.

Investigation of S/N Property on Sputtered Metal Films

II. Experiments and Results Samples were prepared using an RF magnetron sputtering method. Films consisted of a CoNi magnetic layer and a Cr underlayer. The CoNi grain size was made smaller by reducing the grain size of the Cr crystals in the underlayer. Fig. 1 shows SEM photos of CoNi surfaces. We shall refer to the sample with larger grains, at 750 A, as type A film, while the sample with smaller 550-A grains is type B. Parameters of the two types of media are shown in Table 1 . Despite the different grain sizes, there is no significant difference in the magnetic properties between the two types of films. The noise spectrum of the type-A medium is shown in Fig.