Co/Pd superlattices was prepared by rf magnetron sputtering method onto glass substrate with the substrate bias voltage (V_B) of +20~-50v. In the films with Ar gas pressure (P_<Ar>) of 40mTorr, in-plane compressive stress was induced and the surface anisotropy energy (Ks) decreased with increasing negative bias voltage (V_B) owing to magnetoelastic effect of CoPd alloy formed at interfaces. Flatness of the interface was improoved in the films with low P_<Ar> and Ks increased owing to the Neel's surface anisotropy.

View full abstract

GdFe compositionally modulated multilayers were prepared by bias-modulated sputtering. Spin flopping appeared in all films. Magnetization process in the films with the period smaller than 200Å was different from that in the films of A≧400Å. The caluculated magnetization curves with pseudo-wall-structure model agreed with the experimental data for the films of A≧600Å. The exchange stiffness constant used for calculations was 6.5×10^<-7>erg/cm. The calculated hysteresises for the films with A≦200Å were different from the experimental ones.

View full abstract

Magnetic properties of Kr-sputtered Th/FeCo multilayers were studied. Perpendicular magnetic anisotropy K_U and coercive force H_C are unproved by Kr-sputtering The perpendicular magnetic anisotropy improvement is discussed from the point of view of a multilayer structure, an inverse magnetostriction effect and single-ion anisotropy. The multilayer structure and the internal stress are not changed by the Kr-sputtering. K_U improvement with Kr-sputtering is not observed in Gd/FeCo multilayers. Therefore. K_U improvement with Kr-sputtering is caused by the single-ion anisotropy improvement.

View full abstract

Thermal stability and reliability of Pt/Co multilayered films were studied by means of bulk anneling and accelerated tests. The films with ZnO, Pt and AlN underlayers were annealed at the temperature range of 100-400℃ for 30min, in a vacuum of pressure lower than 2×10^<-4>Torr. The films sputtered on ZnO or Pt underlayers exhibited higher stability and, especially, the films with ZnO exhibited perfect hysteresys loop even after anneling at 400℃. Pt/Co MO disks with ZnO underlayers were examined with accelerated tests on the conditions of 65℃-85% RH and 80℃-85% RH. After aging for 2000h at 80℃-85% RH, CNR scarcely lowered and BLER increased because of extra noise. In conclusion, the Pt/Co films with ZnO underlayers have a high reliability and stability.

View full abstract

Spectra of Kerr rotation θ_K and ellipticity η_K of RE-TM are measured systematically. On Gd/Fe based multilayers, magneto-optical effect dependence on bilayer thickness are measured and discussed. The merit of figure of TbFeCo alloy thin film which is used practically and Nd-series/Transition multilayers we suggested is compared and the fact that Nd-series/Transition multilayers is superior to TbFeCo alloy thin film is known

View full abstract

For Gd-Fe/Dy-Fe/Tb-Fe exchange-coupled triple layer films, dependences of exchange coupling on the thickness of the Dy-Fe layer and on temperature are investigated. Interface wall energy density decreases with increasing the thickness of the Dy-Fe layer, and becomes constant for the thickness more than 100 - 150Å. It is found that when the thickness of the Dy-Fe layer is less than 50Å, exchange force to the Gd-Fe layer remains at the Curie temperature of Dy-Fe. Taking account of results of simulation using the molecular field theory, the reason for that exchange force is supposed to be an ordering of magnetic moments in the Dy-Fe layer by molecular field from the adjacent layers as well as atomic diffusion and change of Fe spin.

View full abstract

In order to analyze the write control on optical disk, it is important to clarify the thermal transmission in multilayer. When adopting the mark length recording to magneto-optical disk, the thermal transmission on magneto-optical media is clarified and the factor which decide the thermal transmission on recording layer is analyzed. Based on the thermal transmission, the function of the proposed write control method which can control the edge position of mark is described. The relation between the wave form of write control and the characteristic of multilayer is deduced.

View full abstract

We compared between 1-7 modulation and 2-7 modulation from reproducing jitter about mark-edge recording. We contrived a transmission line model including transmission characteristics of the optical system, and optimized equalization parameters by getting a maximum phase-margin. Total jitter, that determines an error rate, should be treated as a sum of the noise jitter and edge-shifts. As the results of analysis, those reproducing band-width, in the case of minimum total jitter, are almost same as the two modulation schemes. Besides, we found that the total jitter of 1-7 modulation was smaller than that of 2-7 modulation by the ratio of detection windows.

View full abstract

In the light intensity modulated overwriting method with exchange coupled multilayers, the erasing area surrounds the writing area because the erasing temperature is lower than the writing temperature. Therefore, the data on the adjacent track might accidentally be erased when informations are recorded on a track at a high track density. This Thermal Cross-Talk(TCT) can be effectively reduced by controlling write pulse shape and by applying a UV-resin coating on the top of the disk. By such measures, a high track density up to 1.35μm track pitch was proved feasible.

View full abstract

The design of the direct overwrite magneto-optical disk with the exchange-coupled quadrilayer film using light intensity modulation is described. The relation between the overwrite characteristics and the magnetic properties of each layer was investigated. The writing sensitivity for the high power and the low power depended on the Curie temperature of the writing layer and the memory layer respectively. This system possesses a fairly wide composition tolerance, especially RE content for each layer

View full abstract