Thermal stability of longitudinal and perpendicular recording media obtained by Monte Carlo simulation (abstract)

The thermal stability of longitudinal and perpendicular recording media was investigated using Monte Carlo simulation method.¹² In longitudinal recording, the easy directions of the grains are distributed randomly in the film plane. In perpendicular recording, the easy directions are aligned almost perpendicular to the film plane. The material parameters, $M_s$ =400 emu/${\mathrm{cm}}^3,$ $K_u$ =2 ×${10}^6\hspace{0.5em}{\mathrm{erg/cm}}^3,$ and α=1, were used. The exchange stiffness constant between adjacent grains was assumed to be zero. The effects of thickness, grain size in-plane, and distribution of grain size in-plane of the media on decay of the magnetic properties and on decay of the output signal with time were calculated. The rate of signal decay of a longitudinal medium is similar to the decay rate of the squareness and it is much smaller than the decay rate of the coercivity. The same relationship holds for a perpendicular medium. In longitudinal recording, a high density signal is more affected by thermal fluctuation than a low density signal, but in perpendicular recording, a low density signal is more affected than a high density signal. Signal decay is larger in longitudinal recording than in perpendicular recording when the thickness is larger than the grain size in-plane. On the other hand, it is smaller in longitudinal recording than in perpendicular recording when the grain size in-plane is larger than the thickness. The distribution of the grain size in-plane decreases coercivity and squareness of the media at a finite temperature and it also decreases the signal.