Yoshibumi Matsuda

Investigation of 2 Gb/in/sup 2/ magnetic recording at a track density of 17 kTPI

Developments of magnetic head, recording medium, positioning, and signal processing technologies made it possible to perform magnetic recording at an areal density of 2 Gb/in/sup 2/ on a prototype 3.5-in diameter hard disk drive. A track density of 17 kTPI, which is comparable to or even greater than that used in optical storage systems, is used to minimize the reduction in the physical clearance between the medium and the head. The authors outline the system and its component technologies. The read/write characteristics of the 3.5-in prototype disk system are also reported. >

Modulation and crystallographic orientation of sputtered CoNi/Cr disks for longitudinal recording

Origins of readback signal modulation are investigated. Modulation is proportional to the amount of magnetic anisotropy energy and the effects of the magnetic field up to 50 Oe and substrate rotation up to 30 rpm on the modulation are negligible. Average in-plane magnetic properties of CoNi/Cr films are determined by the ( 10\bar{1}1 ) preferred orientation of CoNi films which are epitaxially grown on

Electron spectroscopic imaging analysis of compositional inhomogeneity in CoCrTa longitudinal thin film media

The topographical nature of the compositional inhomogeneity in Co-17at.%Cr-5at.%Ta/Cr longitudinal thin film media deposited at different substrate temperature Ts, was analyzed using electron spectroscopic imaging. In the CoCrTa film deposited at high Ts, Cr segregates to the grain boundaries and intragrains, resulting in a two-dimensional network. The compositional variation grew as Ts became high. The concentration of the Cr enriched region was in the range 20-30 at.%, and that of the Cr depleted region was in the range 5-10 at.% for the sample Ts=270/spl deg/C. A strain-free CoCrTa(11.

Reduction of Co–Cr–Pt media noise by addition of Ti to Cr underlayer

Effects of Ti addition to a Cr underlayer on the magnetic and crystallographic properties of Co–Cr–Pt media were investigated. C/Co–Cr20–Pt (Pt: 8 and 12 at. %)/Cr–Ti (Ti: 0–30 at. %) films were deposited on textured Ni–P/Al–Mg substrates by dc magnetron sputtering. In‐plane Hc and S* increased as Ti was added to the Cr underlayer. The media noise at 167 kFCI decreased with an increase of the Ti content from 0 to 20 at. %. The normalized media noise of Co72Cr20Pt8/Cr75Ti25 media was 20% lower than that of Co68Cr20Pt12/Cr90Ti10 media where their coercivity and S* were almost the same. Further increase of the Ti caused the increase of the media noise. Transmission electron microscopy studies showed that average grain size of Cr–Ti films decreased from 30 to 20 nm with the increase of the Ti content from 0 to 20 at. %. The activation volume of Co68Cr20Pt12 films measured from the time dependences of remanence coercivity decreased by 30% as the Ti content increased from 0 to 20 at. %. The reduction of media n...

Magnetization structures of tracks recorded on longitudinal thin film medium

The authors report the use of a magnetic force microscope (MFM) to study the magnetization structure of a medium recorded using two types of magnetic heads of which track widths are 9.6 and 0.8 mu m. Magnetic interference between the neighboring tracks is investigated by changing the guard-band width. A high track per inch (TPI) magnetic recording with the guard-band width well below 1 mu m is possible by improving the magnetic head field distribution. >

Read and write characteristics of Co-Ni-Zr-M/Cr thin films for longitudinal recording

The magnetic and crystallographic properties and read and write characteristics of sputtered C/Co-Ni-Zr/Cr and C/Co-Ni-Zr-M/Cr (M=V, Nb, Ta, Cr, Mo, W, Cu, Si, Al, Ru and Pt) thin films are investigated. The saturation magnetic flux density B/sub s/ of all C/Co-Ni-Zr-M/Cr films decreases as the amount of additive element increases. The coercivity of C/Co-Ni-Zr-Cr/Cr and C/Co-Ni-Zr-Pt/Cr is higher than that of C/Co-Ni-Zr/Cr films with comparable B/sub s/. The larger the perpendicular anisotropy K/sub p/ and the smaller the anisotropy constant K/sub n/, the lower the media noise N and the higher the S/N ratio. The reduction of K/sub n/ and N are strongly connected to grain separation and grain size reduction. The larger the B/sub s/.tmag, the higher E/sub II/ and N and the lower D/sub 50/ and the S/N ratio. All films except those with Si, Ru, and Pt additives have large K/sub p/, a small K/sub n/, and a high S/N ratio. In particular, C/Co-Ni-Zr-M/Cr (M=Cr, Mo, W, and Al) disks have a better S/N ratio and D/sub 50/ than C/Co-Ni-Zr/Cr disks. >

Magnetic properties and corrosion-resistance of sputtered Co-Ni and Co-Ni-M films for longitudinal recording

The magnetic properties and corrosion resistance of sputtered Co-Ni/Cr and Co-Ni-M/Cr (M=Zr,Cr, Mo,Pt) thin films are investigated. Although pitting corrosion occurs on Co-Ni, Co-Ni-Mo, Co-Ni-Cr, and Co-Ni-Pt films for 1 mol/l NaCl spray tests, Co-Ni-Zr film exhibits almost no pitting because of total surface passivation. Furthermore, Co-Ni-Zr/Cr films show relatively high magnetization, high coercive force, and high squareness, which are suitable for longitudinal recording.

Magnetic and microstructural properties of CoCrPt/CoCrPtSi dual‐layered magnetic recording media

The magnetic properties of CoCrPt/CoCrPtSi dual‐magnetic‐layered thin films are investigated in terms of the crystalline microstructures using a vibrating‐sample magnometer, transmission electron microscope, and scanning electron microscope. The magnetic crystal grains of the films are aligned with forming chainlike clusters. Each stacked magnetic crystal grain is epitaxially grown on individually isolated columnar Cr crystals with a relationship of hcp (1011)Co‐based alloy //bcc (110)Cr. The direction of magnetic easy axes of two stacked magnetic crystals are aligned in a same direction. Single‐crystalline dual‐magnetic‐layered thin films, which are epitaxially grown on MgO(110) single‐crystal substrates, are prepared to estimate the Ku of the dual‐layered magnetic grains. The Ku is determined to be 4×106 erg/cm3, whose value is about 2 times as large as that of single‐layered CoCrPtSi. This large anisotropy energy is presumed to lead the increase of Hc in the dual‐layered magnetic films.

Magnetic and crystallographic properties of sputtered Co-Ni-Zr films on Cr, Mo and W underlayer

Read and write characteristics and magnetic and crystallographic properties of sputtered Co-Ni-Zr on Cr, Mo, and W underlayers are investigated. The crystal grains of the underlayer and the magnetic layer are rice-like and consist of 2 to 10 columnar subgrains. The coercivity of composite films depends on the size of subgrains, reaching a maximum when the magnetic crystal size is about 40 nm. Media noise is proportional to the square root of the length of the rice-like grains; this can be explained by particle-noise theory. >

A Magnetic Force Microscope Using an Optical Lever Sensor and Its Application to Longitudinal Recording Media

A magnetic force microscope (MFM) is developed, which is capable of operation in both DC and AC detection modes, to allow observation of topographic and magnetic structures in the same sample area. An optical lever sensor is introduced to measure the cantilever displacement. DC detection senses the repulsive atomic force between the tip and a sample to provide surface topography information. AC detection senses the force gradient acting on an oscillating tip in the stray magnetic field emanating from the sample to provide magnetic information. A fabrication method for a sharp magnetic tips is also described. A comparison of the magnetization and surface structure images of a thin film medium observed by the MFM shows that nanometer-level roughness on the medium surface can affect the magnetic recording process.