Lessons from research of perpendicular magnetic recording

Lessons from research of perpendicular magnetic recording are presented in this paper. The historical view of the developments in magnetic recording teaches us the "20-year rule" for technical developments and the "40-year rule" for technical evolutions. The research work in perpendicular magnetic recording also fruited with a new concept of classification of research work, which consists of three cyclic research models: creation, development, and integration.