Recently, laminated antiferromagnetically coupled (LAC) media were introduced to overcome the thermal stability issues of longitudinal recording. It is proven that this media shows a better thermal stability at lower Mrδ values. However, there has been some controversy in the origin of thermal stability. Lohau et al. (Appl. Phys. Lett. vol.78, p.2748 (2001)) has reported that the thermal stability of LAC media is independent of bottom layer thickness. Theories based on single-grain also indicate the thermal stability is determined by the top layer properties and the antiferromagnetic coupling constant, J. On the other hand, there are some experimental studies, which indicate that the bottom layer parameters contribute very much to thermal stability. At present, there is no clear understanding on the origin of improved thermal stability in LAC media. In order to extend the life of longitudinal recording, it is essential to understand the origin of improved thermal stability in LAC media. Therefore, in this study, we carry out experiments to understand the thermal stability in LAC media.