Morio Nakatani

Study of Power Calibration Using a Wobbled Track on the Magneto Optical Disk

With increasing optical disk density, land/groove recording has become mainstream and accordinglytrack pitch has continued to become narrower. Therefore, to further increase recording density, it is essential to reduce cross talk and cross erase. In a system optimal recording power is required for recording. However, to determine the optimal recording power, it is necessary to evaluate cross erase characteristics in addition to recording power characteristics, which requires a complicated procedure. We have devised a recording power calibration method using a wobbled track. As a result, it was demonstrated that it is possible to determine the optimal recording power by recording and read-out a monosignal using a wobbled track to calibrate the recording power and observing a sideband wave that accompanies a mono signal. With this method, a considerable amount of work, which was needed to determine the optimal recording power, is no longer necessary. Instead it has become possible to determine optimal recording power with a simple procedure.

Magnetic and magnetooptical properties of Co-Al alloy thin films on a nanostructured substrate

We investigated magnetic and magnetooptical properties of Co-Al magnetic thin films on a nanostructured substrate. The nanostructured substrate was made of polycarbonate by injection molding. The stamper was made by electron beam cutting. The nanostructured substrate contributed a perpendicular magnetic anisotropy component to the film and decreased the reflectance of the film. The Kerr rotation angle on the nanostructured substrate was greater than that on a glass substrate.

The reliability test of center-aperture-detection-type magnetically induced super-resolution magneto-optical disk

The Center Aperture Detection (CAD) type Magnetically Induced Super-resolution (MSR) Magneto-optical Disk is one of method to overcome the limitation of optical resolution. For a reliability of the disk, it is important to investigate the stability of the magneto-static coupling between a readout layer and a recording layer through readout characteristics. In this paper, we tested the reliability of CAD tMSR magneto-optical disk. We used iD PHOTO disk for the CAD MSR magneto-optical disk. In the disk, the data is recorded on land and groove with a track pit of 0.6 µm and a bit length of 0.235 µm, by a method of laser pumped magnetic field modulation with an optical pickup of NA=0.62, λ=650 nm. The reliability was examined by PI error lines under the test condition of 80 °C-90 %RH. There were no considerable changes in read/write characteristics up to with an aging time of 2000 hour. The lifetime of the disk was estimated more than 7000 hour under the condition. By a method of the Arrhenius plots, we assumed that the lifetime of the disk would be more than 100 years under the condition of room temperature. We also confirmed that there were no significant changes in mechanical characteristics of the disks. These results show the disk using magneto-static coupling has sufficient reliability for consumer use.