A micromagnetic Monte Carlo simulation is developed to stud.), the thermal decay and erasure process for perpendicular recording media. The switching probability is calculated based on both the energy barrier analysis and the master equation. The results show that for current head media combination at 1 Tb/in(2), the erasure is severe for the neighboring tracks unless the bit-aspect ratio is increased. The magnetic write width for both side shielded (SS) and no side shield (NSS) head is about the same. The erase band for the SS write head is significantly smaller (20 run less) than that for the NSS head, corresponding to 10 nm or 12% track pitch reduction.