Yasushi Sakai

CoPtCr-SiO/sub 2/ granular media for high density perpendicular recording

A well isolated fine grain structure with large perpendicular magnetic anisotropy K/sub u/ is strongly required for CoCr based high density perpendicular recording media, in order to achieve low media noise performance and high thermal stability. A CoPtCrO magnetic layer has been proposed to enhance the segregated grains with an oxygen-rich grain boundary structure. The authors have already reported that the addition of SiO/sub 2/ to the CoPtCr recording layer is very effective in realizing a well isolated grain structure together with large K/sub u/ value, and also excellent recording performance and thermal stability. In this study, the microstructure, magnetic properties, and recording performance of the CoPtCr-SiO/sub 2/ perpendicular media are discussed in relation to the realization of high density recording media.

Magnetic properties, magnetic cluster size and read-write performance of CoPtCr-SiO/sub 2/ perpendicular recording media

In this study, we investigated magnetic properties, magnetic cluster size of CoPtCr-SiO/sub 2/ media and its read-write performance.

Exchange-coupled IrMn/CoZrNb soft underlayers for perpendicular recording media

An antiferromagnetic Ir-Mn pinning layer was applied to reduce the spike noise that originates from domain walls in a Co-Zr-Nb soft magnetic layer of perpendicular recording media. Blocking temperature was 285/spl deg/C and exchange-coupling energy of 0.22 erg/cm/sup 2/ was obtained by arranging a Co-Fe layer between Ir-Mn and Co-Zr-Nb films, without any thermal treatments to enhance the exchange-coupling field. Spike noise was successfully reduced over the entire disk area using a rapid thermal annealing process, and the total amount of noise generated from a soft magnetic layer decreased as the exchange bias field increased.

Recording performance of the perpendicular recording media with an electroless-plated Ni-P soft magnetic underlayer

An electroless-plated ferromagnetic Ni-P layer, which is suitable for mass production, was employed as a soft magnetic underlayer (SUL) for a double-layered perpendicular recording media. A Ni-P SUL with a thickness range from 1.5 to 3.0 /spl mu/m was plated on the Al substrate, then the surface of the Ni-P SUL was polished about 1 /spl mu/m to obtain a smooth surface with a roughness Ra of less than 0.3 nm. The saturation flux density B/sub s/ and the in-plane coercivity H/sub c/ for the Ni-P SUL were about 0.5 T and 15/spl sim/20 Oe, respectively. Media with a Ni-P SUL at a thickness of more than 0.5 /spl mu/m showed almost the same magnetic properties and recording performances as a medium with a 200-nm thick sputtered CoZrNb SUL. Furthermore, the spike noise commonly observed from an SUL was not found for the media with the Ni-P SUL in this study, indicating great potential for the electroless-plated ferromagnetic Ni-P layer as the SUL of the perpendicular recording media.

Recording performance of double-layered perpendicular recording media with an antiferromagnetic layer

In this study, we have investigated the layer structure and the materials of AFML to obtain high exchange bias field H/sub ex/, and also discussed the influence of the H/sub ex/ to the recording performance for double-layered perpendicular media.

High exchange bias field and low noise IrMn/CoZrNb layers achieved by rapid thermal annealing for perpendicular recording media

Summary form only given. The development of perpendicular HDDs has been constrained by the spike noise that originates from domain walls in soft magnetic layers. An antiferromagnetic (AFM) pinning layer is considered effective to reduce the noise (S. Watanabe et al, Proc. 2001 IEICE gen. conf., vol. 5, p. 35, 2001). However, it is not easy to obtain high exchange bias field (Hex) which is high enough to evade the spike noise. In this study, we reported on low noise media fabricated by the process tailored for mass production. An IrMn AFM layer and rapid thermal annealing (RTA) were employed in the process.

MFM analysis of recorded bit patterns of perpendicular media

Abstract Read/write characteristics of a perpendicular double-layered medium with various thicknesses of soft magnetic layer δsoft using a ring head were investigated by analyzing the MFM image of the recorded bit pattern and reproduced waveform. It was found that the recording bits were written by the field of the head gap for the medium with δsoft of 20xa0nm and whole plane of the write pole for the medium with δsoft of 200xa0nm. It was also found that the bit pattern is disturbed by re-writing in recorded domain for the medium with δsoft of 20xa0nm and the track width expands for the medium with δsoft of 200xa0nm because of the effect of the head skew angle. The SNR of the medium with δsoft of 200xa0nm was 5xa0dB higher than that with δsoft 20xa0nm at a bit length of 0.5xa0μm.

High resolution MFM observation of recorded patterns of perpendicular magnetic recording media in ultra high density

In this paper we analyzed a recording resolution and noise of perpendicular magnetic recording media with various layer thickness by MFM measurement of recording pattern with various linear recording densities.