The magnetic viscosity of unoriented and oriented barium ferrite media has been investigated in order to understand the mechanism of magnetic reversal. The activation volume of magnetic reversal for the unoriented medium gradually increases with increasing test field. In contrast, the activation volumes for the oriented media depend on their degree of orientation. In the media with relatively low orientation, the activation volumes increase sharply in narrow field regions. In the highly oriented media, however, the amount of demagnetization varies non-linearly against ln(t) and the activation volume cannot be obtained as a function of field. In these cases, Richter-type demagnetization curves are obtained. The correlations between medium noise and viscosity characteristics for obliquely evaporated Co films are also described.

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In order to realize an ultra high linear recording density in perpendicular magnetic recording, it is necessary to use a very thin main pole film for a single-pole type head. Since saturation recording becomes difficult for such a very thin main pole, an Fe based material with high saturation magnetic flux density is required to be used. It has been found that the optimum deposition condition to obtain a very soft magnetic Fe-Si-N film changes as the film thickness varies. A high permeability about 3000 for the 50nm thickness Fe-Si-N thin film has been finally obtained by applying the uniform and weak magnetic field parallel to the substrate and using the rf non-magnetron sputtering method with no leakage magnetic flux from the target.

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Co-Cr film with high perpendicular coercivity were prepared using recently proposed low temperature sputter-deposition at a high Ar pressure. A high coercivity of 1370 Oe was obtained by choosing thicknesses of both the Co-Cr layer and the Ti underlayer. Although the Co-Cr layer shows a thin initial growing layer with a low perpendicular anisotropy, the layer exhibits a high crystal orientation though hetero-epitaxial growth on the Ti underlayer. By contrast with conventionally sputter-deposited Co-Cr films, the present Co-Cr layer has a fine columnar structure with voided grain boundaries and with no noticeable Cr segregation in the grains. The voided grain boundary structure could be responsible for the high coercivity in the film. Moreover, oxide of Cr was indicated to be located at the grain boundaries. The proposed low temperature deposition would be a promising method for fabrication of high performance perpendicular magnetic recording media.

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A spacing from a medium to a head is one of the most important parameter on the magnetic recording channel in order to increase the recording density;. We think that the spacing might be measured by the accurate measurement of the modulation noise neighbored on carrier caused by spacing fluctuation. As a result of the investigation, the modulation noise is given from the reproducing theory considered the spacing fluctuation, and the spacing can be calculated from the reproduced signals. Measuring the spacing in several tape head systems, we show the relationship between the spacing and the Rrms of tape, and the relationship between the playback envelopes and the spacing.

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Interparticle interaction in magnetic recording media affects the recording characteristics, in particular the noise characteristics. Therefore we have tried to explain the interparticle interaction by using the mean field theory and estimated the mean field strength in particle coating media by simulation and measurement using a double-coil VSM. However, to consider the interparticles magnetic interaction more strictly in the simulation, it is necessary to study interaction effect in each particles directly instead of the mean field. Therefore we have made a new simulator based on the curling model and an direct calculation method of each interparticle interaction field, and have examined how the interaction affects the magnetic characteristics in longitudinal and perpendicular thin-film media.

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In perpendicular magnetic recording, closed magnetic pathes are formed by a SPT head combining a double-layered hard disk. The easy axis of the medium soft-magnetic backlayer is induced in the disk diameter direction, and the axis Points to the applied field direction from the target source. It is confirmed that the inductance and the readback sensitivity of the head change according to the head return-path structure.

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