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, alpha-Fe2O3 We employed delta M as an indication of magnetic interaction. delta M reduced with decreasing packing fraction. The reduction was much, larger for the 0.10 mu m particle than 0.25 mu m particle. This result suggests that the 0.10 mu m particle and 0.25 mu m particle have different structures, which was confirmed by using a dark-field microscope. The tape using 0.10 mu m particle had higher AC erase noise than DC erase noise because of high magnetization and high coercive force. Whereas, AC erase noise was lower than DC erase noise for 0.25 mu m particle. AC erase noise could be decreased by diluting with nonmagnetic powder for 0.10 mu m particle. Shoulder noise of the signal was also decreased by diluting and the reduction was twice that of output reduction. Plausible explanation of noise reduction is clearness of border on recording pattern, and was confirmed with MFM. From the result of angular dependence of Dc, it is suggested that magnetic reversal mode changed with packing fraction on 0.10 mu m particle, and this conversion may affect characteristic of tape noise.