Fumiyoshi Kirino

Single ion model for perpendicular magnetic anisotropy in RE-TM amorphous films

To investigate the mechanism of perpendicular magnetic anisotropy K u in rare earth-transition metal amorphous films, K u was measured for (Gd 0.75 R 0.25 ) 19 Co 81 films with varying the rare earth element R. Results were analysed based on a single ion anisotropy model using a point charge approximation. The dependence of K u on rare earth element is well explained with the single ion anisotropy. A model was proposed in which anelastic deformation during deposition of the film is responsible for the induction of K u . Magnetostriction can also be explained with a point charge model with screening.

Write control method for high density magneto-optical disk system

In order to increase recording density, mark length recording is superior to mark position recording. However, in the case of magnetooptical media it is difficult to control mark edge position and shape because of its higher thermal conductivity. A new write control method using the multiple pulse write waveform is proposed, and it is shown that high density of 880 Mb/in/sup 2/ can be realized using this write control method. >

Titanium disulfide films fabricated by plasma CVD

Abstract Titanium disulfide films are fabricated by plasma-enhanced chemical vapour deposition using TiCl 4 and H 2 S as source gases. The fabricated films have a nearly stoichiometric composition and preferred orientation whereby crystallographic c-axis is parallel to the substrate plane. The chemical diffusion coefficient of lithium in Ti 1.02 S 2 film was found to be 10 −11 - 10 −9 cm 2 /s depending on the lithium concentration. The activation energy of diffusion was found to be 30–60 kJ/mol. In addition, the secondary battery performance of thin film solid-state cell, Li/Li 3.6 Si 0.6 P 0.4 O 4 /TiS 2 was studied.

Precise Mark Shape Control in Mark Length Recording on Magnetooptical Disk

To realize higher storage density on a magnetooptical disk, we proposed the write control method, which controls shapes of recorded mark in marks length recording. In this paper, the analysis of this write control method is reported. Based on the model of the recording process, we discuss the necessary condition of the recording pulse waveform for the control of the recorded mark shape on magnetooptical recording media which have large heat conductivity. The write control method is examined under the condition of 880 Mb/in2 recording density. The precise control of the recording mark shape is confirmed through the experiment. From the result of the computer simulation, it is proven that this method satisfies the necessary condition, which clarified the effect of this method theoretically.

Study on high reliability TbFeCoNb magneto‐optical recording disk

We studied the magnetic properties, corrosion resistance, and disk properties, using TbFeCoNb film for magneto‐optical film. Adding 2–3 at. % Nb to TbFeCo, the magnetic properties did not change, and the recorded domain on the disk using TbFeCoNb film is the same as on a TbFeCo film. TbFeCoNb film has high corrosion resistance for wet corrosion and pitting corrosion. The dependency of corrosion on the forming process is studied. The magnetic properties are dependent on the process such as rotational process and pass‐by process, but the corrosion resistance is independent. As a result, we have a high reliability and high‐performance magneto‐optical disk. Write/erase repetition cycles are more than 107. After this disk was held in 60 °C−90% RH (relative humidity) for 2000 h, carrier‐to‐noise ratio (C/N), and defect error rate had not changed.

High corrosion-resistant magneto-optical film on a new plastic substrate

To realize high-data-rate and high-reliability magnetooptical (MO) disks, a corrosion-resistant MO film and a novel plastic substrate were developed. Corrosion was reduced by adding a metallic element (M=Ti,Nb,Ta,Cr) to TbFeCo film. The magnetic characteristics of TbFeCoM film were designed to be the same as those of the TbFeCo film. The plastic substrate (photocurable casting resin, PHC) shows low retardation and high heat resistance. MO disks with a trilayer structure on PHC showed high reliability even in severe conditions. The performance of a prototype MO recording system using the PHC disk is presented. >

Magneto-Optical Disk Structure with High Write/Erase Repeatability

Over 107 write/erase repeatability has been achieved in magneto-optical (MO) disk by optimizing thermo-structural design through thermal conduction analyses. By combining this technology with that for anti-corrosion measures, a highly reliable and durable 5 1/4 inch MO disk has been developed. Carrier level degradation through write/erase repetition, which was observed in the cource of the development, is thought to be interpreted as a structure relaxation by annealing leading to a localized change in magnetic properties.

Influence of seedlayer on film microstructure of Co-Cr-Pt longitudinal recording media fabricated on plastic substrates

Influences of seedlayer on surface and cross-sectional film structures are investigated for the magnetic recording media fabricated on a plastic disk substrate. An irregular film growth is observed when a recording medium consisting of C/Co-Cr-Pt/Cr-Ti multilayer is deposited directly on an amorphous polyolefin substrate. Zr or Ti seedlayer with HCP crystal structure is found to be useful in improving the film microstructure and is comparable to that formed on a glass substrate. The recording media with Zr or Ti seedlayer have desirable microstructure and surface flatness which are necessary for high density magnetic recording applications.

Magneto-optical recording media of GD based amorphous alloy systems with high kerr rotation

To obtain practical magnetooptical materials having large Kerr rotation Θk, high perpendicular coercivity Hc and relatively low Curie temperature Tc( \sim200\deg C), rare-earth elements having a one-ion anisotropy were added to Gd-Fe-Co amorphous alloy system, which has a large intrinsic Kerr rotation but an in-plain anisotropy. As a result, replacing Gd by Tb,Dy,Ho, a large perpendicular anisotropy Ku is induced associating with the increase of Hc. With the optimization of their compositions, Gd-R-Fe-Co (R=Tb,Dy,Ho) amorphous films with Θk= 0.42-0.45° (at the wavelength of 822nm), Tc \sim200\deg C, and Hc=160-400 kA/m(2-5 kOe) were obtained.

Thermomagnetic recording mechanism on TbFeCo disks

Abstract In order to make clear a domain formation mechanism in magneto-optical disk with TbFeCo amorphous film, a numerical simulation based on a heat flow analysis is reviewed and discussed. In a conventional laser-power-modulation method, diameters of circular domains are calculated by using forces acting on the domain wall. Calculated change of the diameter with laser power agrees with optically observed results. Moreover, the shape of chevron type domains for a magnetic-field-modulation method can be explained by using the same simulation methods.