We have investigated fabrication method of Co-Cr/Ni-Fe-Nb double layer media. In order to get the high deposition rate of Ni-Fe-Nb film as an under layer, an aluminum chammber was utilized in a sputtering system associated with Plasma Enclosed Target (PE target). The sputtering apparatus with the chamber could reach high vacuum in shorter time than a conventional one with a stainless chamber. Soft magnetic properties and crystalline structure of the deposited films were improved. Based on these results, we fabricated perpendicular double layer media with the Ni-Fe-Nb under layer deposited with new chamber sputtering apparatus. The media had smoother surface and better recording performance compared with the media fabricated with a conventional sputtering apparatus of a stainless chamber.

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The correlation between magnetic viscosity and medium noise in CoCrTa and CoCrPt longitudinal thin-film media was investigated by measuring the time dependence of remanence coercivity H_r and the read/write characteristics. The media were prepared by dc magnetron sputtering under various conditions. Fluctuation fields H_f of magnetic viscosity at H/H_r=1 were obtained from the slopes of H_r versus 1n t plots. Medium noise decreases with kT/H_f (= the product of activation volume and saturation magnetization per unit volume). Medium noise thus primarily depends on the size of the minimum unit of the magnetic moment in reversal.

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The recording performance of Co-Cr-Nb and Co-Cr-Ta perpendicular media was evaluated. Single layer media and double layer media were recorded by using a ring head and an SPT head, respectively. Both the Co-Cr-Nb media and the Co-Cr-Ta media exhibited similar high density responses, in the case of single layer and double layer states. Maximum recording densities were obtained at 720 kFRPI for the single layer media and 800 kFRPI for the double layer media. It was found that the noise level for Co-Cr-Nb media was lower than that for Co-Cr-Ta media by the factor of 5 dB for the single layer media.

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To achieve higher track density in longitudinal recording, the degraded side written band width (ΔW) near the track edges is required to be suppressed. This paper introduces a new recording method using tri-layer media (recording layer/non-magnetic layer/soft magnetic layer/substrate) to diminish ΔW. Magneto-static coupling between the soft magnetic layer in the media and the write head poles decreases side fringing field off the track edges. Side written bands made on the tri-layer media were compared with those on conventional monolayer media. Off-track overwrite experiments revealed that the tri-layer media reduced ΔW by 50-70% compared to the mono-layer media with keeping the linear resolution. Both media had almost the same size of effective write track width.

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It is necessary to use excellent soft magnetic materials of extremely small size for a perpendicular recording head to obtain an ultra high recording density. We have investigated permeability of nonlaminated and bilaminated soft magnetic film strips with thickness of less than 60 μm. For the nonlaminated film strips, a high permeability is obtained in the thinnest strips with the smallest saturation magnetization, but it decreases monotonically with narrowering the strip width, W, then approaches unity at around W=10-20 μm. On the other band, the changes in permeability is not monotonic for the bilaminated film strip, and a partial response of the magnetization could be observed for the narrow strips with the width of less than 10 μm.

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Read/write sensitivity of a single pole head has been improved by introducing laminated thin film coil. This head has a very low impedance which is effective for high frequency operation, though its absolute output is not large because of few numbers of the coil. In this report the absolute output of the head is doubled by increasing the number of turns into two. Eddy current effect in the laminated thin film coil has also been investigated.

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