Dependence of field gradient on media noise was demonstrated. Medium noise was worsened by influence of secondary field, when the field gradient of the secondary field is considered to be the dullest one. The influence was confirmed by the investigation of change of media noise, which is based on the intrinsic micromagnetic media properties, against different field gradients. Reverse DC modulation noise and transition noise of low Hc and high Hc disks were evaluated by using a single sided MIG and a ferrite mini-monolithic head. The reverse DC modulation noises showed a different value for each head in spite of the same medium. The increasing ratio of the reverse DC demagnetized noise to the DC saturated noise, i. e., reverse DC modulation ratio, showed higher value when the medium was evaluated by using the MIG head which can generate a sharper field gradient in each medium. However, the transition noise was smaller by using the MIG head than by using the ferrite head. As a result, both the reverse DC modulation increasing ratio and the transition noise level which was believed to be an intrinsic property of media were strongly correlated to the field gradient.
