Modeling of thin-film media with advanced microstructure for ultrahigh density recording

Magnetic thin films with subgrain structure, or nanocrytalline films are studied via micromagnetic modeling. The subgrain nanocrystallites form a bicrystal structure inside a normal grain, due to proper epitaxial growth. It is shown that a relatively small but nonzero exchange coupling through normal grain boundaries is critical for obtaining high coercive squareness. Maintaining low exchange coupling between subgrains in a normal grain is important for achieving low transition noise. The calculation shows that films with this microstructure can have S*≊0.95 and a signal-to-noise ratio of 36 dB at 385 KFCI with 1-μm track width. Such film microstructure is practically achievable in principle and is suited for future high recording density applications.