I ) Advanced Tape Div., Httachi Maxell, 1 Koizumi, Oyamazaki. Otokuni, Kyoto 618-8525, Japan (2) Development & Technology Diu., Hitachi M a d , t Koizumi, Oyamazaki, Otokuni, Kyoto 618-8525, Japanlntroduction When high capacity recording media is fabricated by metal particulate (MP), it needs both very fine particle size and high coercivity [l]. Needle type Fe-based MI' has been suitable for this purpose, however, it becomes difficult to obtain adequate coercivity with these MP whose long axial decreases less than 30 nm. The reason is that its coercivity arises form structural anisotropy, so the long axial size decreasing causes the reduction of both particle aspect ratio and the coercivity. We has developed a nanosized spherical metal particles (NanoCAP) with a very high coercivity up to 3000 Oe, the origin of which is crystalline anisotropy. We also develop a magnetic recording tape with NanoCAP and evaluate its playback performance. In this paper we report the experimental results of developed NanoCAP media.I Experimental NanoCAP media were fabricated as dual coating with magnetic layer thickness of about I OOnm. Playback performance was evaluated by a drum tester with a linear velocity of 3.4 mlsec, using a writer with a track width of 12 pm and a gap length of 170 nm, and a magnetoresistive reader with a track width of 7.5 pm and a shield-to-shield distance of 170 nm. Magnetic properties were measured by a vibrating sample magnetometer.Results and discussions Figure 1 shows the linear recording density dependence on signal to noise ratio(SNR), which indicates sufficient SNR values up to 300 kfci. Noise spectrum after writing of 5 MHz signal is compared with a spectrum of l0Onm MP noise in Fig. 2, those indicate reduced broad-bands noise because of magnetic particle size decreasing. This low-noise results from reduced the square root of particle volume because relative broad band noise has linear dependence on the square root of the particle volume, as shown in Fig. 3.From a roll-off curve, linear density at 50% of the maximum output (D50) of 170 kfci was obtained, A pulse width at half of maximum amplitude (PWSO) of 330 nm was evaluated with isolated pulse at 2.4 kfci. These high-resolution characteristics could come from smooth surface (mean roughness Ra=2.0nm). 30 I a Fig. 1 0 -2 g -4 s -6 -8 -10 ,-30 m rg : : 3 -50 < .--B .70 NanoCAP -90 0 LO 20 100 200 300 L i n a D m i q Wci) F w u a c y W W SNR vs. linear recording density. Ctnsed Fig. 2 Noise spectra of NanoCAP meda (lower) and circle with straight line shows NMoCAP media and closed circle with straight line shows 1 0 0 d P media. lOOnm MP media (upper). 0 50 IO0 150 VIr/ (mn3") Fig. 3 Relative broad band noise (Nbb) vs. square root of the particle volume. Closed circles and closed squre show the noise of NanoCAP media and MP media, respectively.In conclusion, we have successively fablicated NanoCAP coating tape media with adequare SNR value and high resolution.
