Sadao Kadokura

Deposition of Co-Cr films for perpendicular magnetic recording by improved opposing targets sputtering

It is well known that Co-Cr films show a high perpendicular magnetic anisotropy, coercivity higher than 1000 Oe and other properties favorable for perpendicular magnetic recording media. In this report, Co-Cr films were prepared on polyimide films at high deposition rates in the range of 500-4000 A/min using a new type of cathode sputtering apparatus with opposing targets. The deposition rate was 20 times as high as that attained by conventional RF sputtering. The composition of the deposited films was almost same as that of sputtered targets. The X-ray diffractometry indicated that the crystal of the film had hcp structure. The degree of c-axis orientation ΔΘ 50 was as low as 3.0° The prepared films 1 μm thick, deposited at the high rate of 4000 A/min had magnetic properties suitable for perpendicular recording media, such as a perpendicular coercivity of 1100 Oe and an anisotropy magnetic field of 5.7 KOe.

On improved durability characteristics for a Co-Cr flexible disk system

The signal durability of a disk which was formed by sputtering Co-Cr, permalloy, and inorganic protective layers on both surfaces of a flexible substrate was studied by evaluating its tribological characteristics. Out-put signal loss in proportion to head-pass number was found to be due to brittle fracture and/or plastic deformation of the disk. A disk with plastic deformation showed better signal durability than that with brittle fracture. High toughness and homogeneous structure of metal layers presumably improve durability for the practical use of a Co=Cr layered flexible disk system.

Microstructure and Tribological Properties OF Co-Cr thin Films Deposited by Facing Targets Sputtering and Magnetron Sputtering Methods

The tribological properties and the slid surface profiles of Co-Cr thin films deposited by Facing Targets sputtering and Magnetron sputtering methods were investigated in regard to the durability of flexible disks. Co-Cr thin films with columnless microstructure and homogeneously packed particles were much tougher than ones with columnar microstructure for tribological test. The Co-Cr films deposited by conventional Magnetron sputtering method revealed typically columnar structure, while ones deposited by Facing Target sputtering method did columnless microstructure. This indicates probably homogeneous distribution of strong bonding forces between grain boundaries throughout the films, because no brittle fracture was observed even after the delamination between a plastic substrate and the CoOx/ Co-Cr / Ni-Fe triple layers took place by application of excess stresses. It was found that difference in morphology of Co-Cr thin film between Facing Target sputtering and conventional Magnetron sputtering methods was much significant.

Microstructure and noise characteristics of Co-Cr-Ta films on ultraflat glass substrates for longitudinal recording disks

Co–Cr–Ta/Cr bilayered films for longitudinal recording disks were deposited by facing targets sputtering (FTS) on 2.5 in. and ultraflat disk substrates of durable single-crystal silicon at temperature Ts of 100 °C and Ar pressure PAr of 0.2 mTorr. TEM observation of the films revealed ultrafine microstructures, and grain boundaries were unclear. The noise and recording characteristics of those disks were comparable with those of very high-performance disks with Co–Cr–Pt films, with coercivity Hc of 2.4 kOe, employed as a reference, even though the Co–Cr–Ta films exhibited macroscopic Hc of only 800 Oe. In this study, Co85Cr13Ta2/Cr bilayered films with the same composition as the above-mentioned disks were deposited by plasma-enhanced (PEFTS) on 2.5 in. and glass–ceramic substrates with ultraflat surface and tough durability at Ts of 100 °C to obtain better microstructure, signal-to-noise ratio (SNR), and surface flatness, with consequent lower flying height, than those on Si substrates, thus making it po...

Nano-size magnetic crystallite formation in Co-Cr thin films for perpendicular recording media

In order to understand the formation of nano-size magnetic domains in Co/sub 76/Cr/sub 24/ thin films for ultra-high density perpendicular magnetic recording, film thickness and sputtering gas pressures were investigated using a facing target sputtering (FTS) apparatus. Investigations of these films showed thy were composed of highly oriented hcp crystallites with lower Cr content (C/sub Cr/) of isolated ferromagnetic areas uniformly distributed in the higher C/sub Cr/ host paramagnetic matrix. The diameter of the lower C/sub Cr/ areas in these films was between 3-5 nm. The perpendicular coercivity in the surface region was greater than 2400 Oe. Consequently, this film is considered to be a good candidate for perpendicular magnetic recording densities approaching 1000 Kfci (10 Gb/in/sup 2/).