In this study, a new mechanism responsible for the increase in media noise in perpendicular magnetic recording is discussed. We observed that the media noise of a particular linear density drastically increased for some combinations of shielded pole heads and capped media with higher Ms of cap layers and thinner SUL. A MFM observation indicated that the transition jitter increased at a linear density, which correlated with the domain width in the AC-erased region. It was assumed that the reconstruction of the magnetic domains due to the negative field around the trailing shield occurred when the transition period was comparable to the magnetic cluster size. These results indicated that the optimization of the field at the edge of the trailing shield and that of the magnetic characteristics for the cap layer were important for improving the overall R/W performance.