We have developed a novel flying magneto-optic transfer readout head for a hard disk, which has a potential of narrow track readout. This head is composed of a garnet substrate itself and the magnetic garnet film grown on it is used as a readout layer. Straight grooves were formed in the magnetic garnet layer to decrease the noise in readout. When the signal of 2.5 μm wavelength recorded on magnetic disk was read out by using this new head, carrier-to-noise raito of 52dB was obtained. Decrease in readout carrier level was only 3dB, as the track width was decreased from 80μm to 1μm. Crosstalk was about -40dB.
The effect of Pt additives in TbFeCo(Pt)/Pt multilayers on magnetic and magneto-optical properties is investigated. The perpendicular magnetic anisotropy constant K_u of the multilayers becomes larger (〜2.5×10^6 erg/cm^3) with Pt layers than that of a TbFeCo(Pt) single layer. Also, Pt layers are found to contribute significantly to the polar Kerr spectra at ultra-violet photon energies beyond 3 eV. The Kerr rotation θ_K and ellipticity η_K are enhanced with increasing Pt layer-thickness t_<Pt> and become saturated at t_<Pt>=12Å. This result implies that Pt atoms up to about 6Å from the interfaces are contributing to the Kerr activity. The largest enhancement in the Kerr rotation θ_K is found at about 5 eV.
Local structural anisotropy of RE/TM multilayers prepared under different conditions was investigated by using extended X-ray absorption fine structure (EXAFS) spectroscopy to estimate the correlation between Perpendicular magnetic anisotropy and local structural anisotropy. Fourier transformed Fe-EXAFS indicated the difference between atomic pair ordering aligning in the film plane and film normal, showing the existence of structural anisotropy. It was found that the variation of the structural anisotropy well corresponds to that of the perpendicular magnetic anisotropy, both of which change depending on the bilayer period and the preparation condition.
An amplifyed magneto-optical signal readout using a dynamic domain expansion effect was proposed and experimentally confirmed. The packed domain of 0.2-0.4μm were expanded to saturated signal level by using an alternative external readout field of 0.2-0.4μm period. And also a crescent-shaped domains 0.08μm in length were expanded on the expansion readout layer copied from the recording layer under the condition of no alternative external field. These result reviels that the areal recording density of over 10 Gbit/in^2 with a 680-nm- wavelength laser should be realised.
When the writing laser power is higher than 10mW, non-erasable bits are formed in Bisubstituted garnet film. Write-once recording is possible also in the amorphous film which is a precursor of garnet film with laser power lower than this value. In the latter case, minimum bit length is 0.6μm and maximum CN ratio is 46dB when line velocity is 2.5m/s and bit length is 3μm. These results lead to the following attractive and useful applications. That is, the perfect protection of information in a magneto-optical recording medium from magneto-electrical or thermal disturbance, the novel recording material which can be utilized both for write-once recording and magneto-optical recording, and the high sensitive write-once recording material.