Influence of magnetic interaction and particle length on MP tape noise

Some noise characters were measured for MP tapes of different particle size at different packing fraction which is controlled by diluting with nonmagnetic powder, /spl alpha/-Fe/sub 2/O/sub 3/. We employed /spl delta/M as an indication of magnetic interaction. /spl delta/M reduced with decreasing packing fraction. The reduction was much larger for the 0.10 /spl mu/m particle than the 0.25 /spl mu/m particle. This result suggests that the 0.10 /spl mu/m particle and the 0.25 /spl mu/m particle have different structures, which was confirmed by using a dark-field microscope. The tape using the 0.10 /spl mu/m particle had a higher AC erase noise than DC erase noise because of high magnetization and high coercive force. Conversely, AC erase noise was lower than DC erase noise for the 0.25 /spl mu/m particle. AC erase noise could be decreased by diluting with a nonmagnetic powder for the 0.10 /spl mu/m particle. The shoulder noise of the signal was also decreased by diluting and the reduction was twice that of output reduction. A plausible explanation for the noise reduction is the clearness of the border on the recording pattern, and this was confirmed with MFM. From the result of angular dependence of H/sub c/, it is suggested that the magnetic reversal mode changes with packing fraction for the 0.10 /spl mu/m particle, and this conversion may affect tape noise characteristics.