In magneto optical recording, the magnetic field modulation method has been very remarkable on high density recording. However, it has been already reported that in high density recording the shape of recorded domain strongly affects its shorter quality. In particular, In the case of recording magnetic domains of shorter than 0.5μm with magnetic field modulation, it is found that CNR is degraded rapidly by recording over and over again in spite of sufficient alternating magnetic field applied. Then almost the same signal quality with is initial state is obtained by means of the combination of magnetic field modulation and multi LASER pulse.

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Magneto-optical Faraday effect of plastic films in which fine ferromagnetic particles are dispersed, was investigated. For plastic we used PMMA, while for ferromagnet, we chose cobalt. The film preparation procedures are as follows : Dicobalt octacarboneyl (Co_2(CO)_8; shortly DO) was added in a solution of PMMA which was dissolved by toluene. Fine cobalt particles were formed by thermal decomposition by heating the solution at 110℃ for 6 hours in a rotary evaporator. The colloidal solution thus prepared was spin-coated on glass substrates and then dried in the presence or absence of a dc magnetic field. The average particle diameter varied from 7nm to 10nm depending on the DO concentration in PMMA solution. The special features of Faraday effect (rotation θ_F and ellipticity χ_F) of the films are quite different from those of cobalt, and can be controlled artificially by size and agglomerate state of particles.

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We theoretically analyzed the magneto-optic Faraday effect in discontinuous media composed of one-dimensional array of magnetic materials and air gaps. The analysis suggest that, even in the simple discontinuous media with the periodic structure, the Faraday effect varies to a large extent from that in a continuous media. This is explained from the fact that the polarization and the coupling states of two eigenmodes of optical waves in the media change drastically depending on the media structures. This indicates that the magneto-optic Faraday effect of magnetic materials might be able to controlled artificially by introducing the discontinuous structure.

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Magneto-Optical (MO) disks with metal guiding layers are useful for narrowing track pitch and reduction of disk noise compared with conventional pregrooved MO disks. The most suitable production condition of Cr guids, such as exposure power, resist thickness and resist ashing, is derived for the track pitch of 0.85 μm in order to decrease the disk noise and to improve CNR. The maximum CNR of 47 dB and 54 dB were measured at 3.73 MHz and 1.0 MHz for the track pitch of 0.85μm with the conventional optical head having an objective lens of 0.53 NA and a 780-nm laser. The cross-talk were-26 dB and-23 dB at 3.73 MHz and 1.0 MHz, respectively. These results support the prospect that the 8x MO disk of 90 mm can be achieved by using an objective lens of 0.60 NA and a 680-nm laser.

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Amorphous DyFeCo films have been studied for use as magneto-optical storage media for magnetic field modulation direct overwriting. The Dy-rich DyFeCo film has been found b be suitable for magnetic field modulation recording by applying small-modulation magnetic field. The magnitude of the external recording magnetic field required for direct overwriting has been considerably reduced through adjusting the Dy content in DyFeCo film. In addition, the read-write characteristics have been improved by controlling the content of Co in the film. The DyFeCo disk prepared for this study shows the carrier to noise ratio up to 49.5 dB when the modulation magnetic field is about 80 Oe and the recording mark length is 0.83 μm. Furthermore its reliability performance has been examined by the accelerated test.

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TbFeCo magneto-optical single layer disk with different compositions have been investigated for recording of small size domains with 830nm wavelength laser. A low writting stability, dependent on the applied field, was found when recording domains smaller than 0.5 μm on a transition metal rich disk. On the contrary, a high writing stability was achieved on a disk with a highly rare earth rich composition. These phenomena can be explained by using the Huth model for domain formation.

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For Gd-Fe/M/Tb-Fe(M=Dy-Fe, Pt, Pd, Cu) triple layered films. dependences of interface wall energy density on the thickness of intermediate layers and temperature are investigted. The reason for the exchange-coupling caused through the intermediate layer is considered For the Dy-Fe intermediate layer, considering simulation of the interface wall energy density, the reason for the exchange-coupling is an ordering of magnetic moments in the Dy-Fe layer by molecular field from the Gd-Fe and Tb-Fe layers. For the Pt, Pd intermediate layer, considering measurement of magnetic moments of the Pt, Pd layer, the exchange-coupling is caused by the polarization of the Pt, Pd moment. The exchange-coupling through the Cu intermediate layer is supposed not to exist.

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