Heat-Assisted Magnetic Recording Medium Ferrite Grain Boundaries

The patent applies local quality by introducing ferrite specifically at the grain boundaries of magnetic grains, rather than uniformly throughout the entire magnetic layer. This localized placement allows the magnetic grains themselves to maintain fine size for high areal recording density, while the ferrite at grain boundaries provides the necessary thermal stability and Curie temperature uniformity. The ferrite acts as a stabilizing phase at critical locations (grain boundaries) without interfering with the fine grain structure needed for high density.

The patent employs composite materials by combining magnetic grains (with L10 structure) and ferrite in a granular structure. This composite approach allows the magnetic grains to provide high coercivity and fine grain size for high areal recording density, while the ferrite phase contributes to thermal stability and reduces Curie temperature variance. The composite structure of magnetic grains embedded in a ferrite-containing matrix resolves the contradiction between fine grain size and compositional stability.

The ferrite is placed locally at grain boundaries rather than uniformly distributed, allowing magnetic grains to remain fine while gaining thermal stability from the ferrite environment. This localized placement ensures that the Curie temperature is stabilized at the grain boundary regions, which are critical for maintaining uniform thermal characteristics across the magnetic layer.

The ferrite acts as an intermediary material between magnetic grains, mediating the thermal properties. By introducing ferrite at grain boundaries, the patent creates an intermediate phase that buffers thermal variations and stabilizes the Curie temperature, preventing the decrease and variance that would otherwise occur with finer magnetic grains.