Chiseki Haginoya

Nanostructure array fabrication with a size-controllable natural lithography

A simple technique for size-controllable nanostructure array formation has been developed, using self-assembled polystyrene beads whose diameters can be arbitrarily reduced by reactive ion etching. We have produced a hole array of 83 and 157 nm diameter with 200 nm pitch on Si substrate. This technique can find potential applications in many areas of science and technology.

MAGNETIC NANOPARTICLE ARRAY WITH PERPENDICULAR CRYSTAL MAGNETIC ANISOTROPY

By using electron beam lithography, a continuous CoCrPt film with a perpendicular crystal magnetic anisotropy has been patterned into a magnetic nanoparticle array of 29 Gdot/in.2 with a 150 nm period, an 80 nm diameter, and a 44 nm height. Studies of magnetic properties using a magnetic force microscope and a vibrating sample magnetometer show that this patterning increases the remanent-to-saturation magnetization ratio from 0.2 of the continuous film to 1 of the particles, and that each particle has a single magnetic domain with perpendicular anisotropy. The application of this array to future high density magnetic recording media is discussed.

Morphology and photonic band structure modification of polystyrene particle layers by reactive ion etching

Morphology of self-assembled polystyrene particle layers has been modified by reactive ion etching. The etched layers have two-dimensional periodic structures in submicron scale, the period of which is determined by the initial size of the particles, and the shape of the etched particles has been gradually changed to a thinner ellipsoid depending on the etching time. Resonant phenomenon between incident light and electromagnetic eigenmodes of the photonic band of the etched layers has been observed in transmission measurement. The resonant frequencies have gradually shifted according to the etching time, i.e., the photonic band structure of the layers has been successfully modified. Various kinds of applications can be expected due to the electromagnetic resonant phenomenon and the characteristic surface structure of the layers.

Thermally assisted magnetic recording on flux-detectable RE-TM media

We studied a thermally assisted magnetic recording on flux-detectable RE-TM media. This recording scheme has a close affinity with near-field optics such as solid immersion lens (SIL) optics and scanning near-field optical microscope (SNOM)-type optics. The requirements for high-density thermo-magnetic recording and a novel near-field optical head were discussed.

THERMOMAGNETIC WRITING ON 29 GBIT/IN.2 PATTERNED MAGNETIC MEDIA

We have demonstrated a thermomagnetic writing on a 29 Gbit/in.2 patterned medium with perpendicular magnetic anisotropy, by using Joule heat produced by a current flowing between a magnetic dot in the medium and a magnetic force microscope tip. The possible application of this thermomagnetic method to future patterned media is also discussed.

Fabrication process for a trapezoidal main pole for single-pole-type heads

We investigated the fabrication processes used for single-pole-type heads for perpendicular recording. To solve the problem of side write/erase on adjacent tracks, it is necessary to develop a trapezoidal main pole for single-pole-type heads. We therefore proposed two different fabrication processes: (1) a process using electroplating and ion milling and (2) a damascene process using reactive ion etching and chemical mechanical polishing. We made the trapezoidal main pole using the damascene process. An evaluation showed that using a single-pole-type heads with a trapezoidal main pole solved the side write/erase problem. There was also no problem with the writing performance of the heads. To make a narrower track (less than 250-nm wide), we optimized the process conditions.

Side-shielded tunneling magnetoresistive read head for high-density recording

To reduce the side-reading effect and obtain a narrower effective read track width, the side-shield effect was studied by computer simulations and experiments. Computer simulations show that the side shield, which consists of a soft magnet, can reduce the effective read track width. To examine the effect, a side-shielded tunneling magnetoresistive head was fabricated. In the head, to place a soft magnet by the sensor side, a closed-flux structure was applied for longitudinal bias instead of a conventional abutted junction. Microtrack profile measurements agreed with simulated results, and the side-shield effect was clearly demonstrated.

Developments of nanoimprint technologies and applications

The nanoimprint technology is attractive for the fabrication of nano-scale structures in view of cost and mass production. There are several points for the industrial applications such as pattern formation area, resolution, residual layer thickness, precise control of pattern transfer, lifetime of mold, alignment and so on. A thermal nanoimprint system, which can imprint fine dots on a 300 mm diameter wafer in a single step, is developed. The narrow pith patterns for future storage and IT devices are formed on a polymer layer. A high-aspect nanoprint (Hi-NP) technology forms polymer nanopillars with high aspect ratio. The nanopillars are applied to a bio-chip for the fluorescence immunoassay. The chip is effective in the enhancement of the fluorescence intensities, since the nanopillars enlarge the surface area.

Microscopic imaging of Fe magnetic domains exchange-coupled with those in a NiO

We revealed the micromagnetic structure of an Fe thin film exchange interacting with the spins of a fully compensated (001) surface of antiferromagnetic NiO. The interface exchange interaction causes the Fe domains to follow the NiO domains. The Fe spin polarization is in plane and the spin polarization in each domain is roughly perpendicular to an easy-spin axis of the NiO. These results agree with numerically calculated spin directions. Our numerical results also show that the NiO spins at the interface cant from the easy-spin axis towards the Fe spin because of exchange coupling.

Fabrication processing of a trapezoidal main pole of single-pole-type heads

Summary form only given. The perpendicular recording system is considered as one of the most promising techniques to increase the areal density of hard disk drives. However, there is a side write/erase problem to adjacent tracks due to the skew angle of hard disk drives. A trapezoidal main pole of a single-pole-type head is required to improve this problem (S.E. Lambert and B.A. Lairson, PMRC 2000 digest 24aA-2, pp. 131-132, 2000). In this study, we investigated fabrication processing of the trapezoidal main pole.