Atsushi Kikugawa

Thermal stability of magnetic recording in perpendicular thin film media

Recording and signal decay characteristics of perpendicular CoCr-alloy thin film media are investigated in comparison with those of longitudinal media. A perpendicular medium shows recording resolution 25-32% higher than that of a longitudinal medium with similar low density output. The medium S/N of a 25 nm thick perpendicular medium is comparable to that of a 16 nm thick CoCrPt longitudinal medium at high linear densities. The signal decay rate of the high Mr/Ms perpendicular medium is below 0.2% per decade of time for all linear densities. These results and thermal stability considerations based on the temperature dependence of KuV/kT indicate that CoCr-alloy perpendicular recording media are promising to extend the linear density well beyond 400 kFCI.

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. >

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.

Nanometer recording using an atomic force microscope

We demonstrated the feasibility of ultrahigh-density storage by using an atomic force microscope in air to form gold dots tens of nanometers in diameter on a silicon substrate. The probe was prepared by coating a thin gold film onto a SiOg birdbeak-type cantilever fabricated by a silicon microprocess. Gold dots about 15 to 200 nm in diameter could be successfully formed by controlling the applied pulsed voltage between the probe and a silicon substrate covered with a layer of natural silicon dioxide. These results indicate that this technique can be used for recording information at a density greater than 1 Trillion-bit/in2.