Thermal stability of written bits in double-layered perpendicular recording media

The thermal stability of written bits on single- and double-layered perpendicular magnetic recording media were compared from micromagnetic simulation. It was found that, although double-layered media show a higher thermal stability than single-layered media, the difference is not large. Under the calculation conditions used here the gain in thermal stability by double-layering was found to correspond to 7.5% increase in the volume of a magnetic grain. It was also found that this difference tends to decrease at the low and high ends of recording density. Investigation of the magnetostatic field exerted in the recording layer shows that the change in the thermal stability is due to the change in the layer-thickness component of the static field exerted on the recording layer. Although the increase in the dispersion in the easy axes of magnetization was found to decrease thermal stability, the decrease was greater in single-layered films than double-layered films.