Micromagnetic study of effect of media intergranular exchange interaction in perpendicular recording

A micromagnetic study is performed for the writing and reading processes in perpendicular recording at high areal densities. In particular, the effect of intergranular exchange interactions in media is examined. Calculations are done for three different values of intergranular exchange coupling. The calculated media hysteresis loops show that the saturation magnetic field increases when exchange becomes weaker. The writer deep gap field is chosen to be equal to the saturation field so that proper overwrite is assured. Modeling shows that the magnetic cluster domain size becomes larger and the readback signal exhibits larger variation at its peaks when exchange constant increases. The variation of readback signal at its peaks in square wave perpendicular recording is primarily due to the variation of bit cell length of written patterns. On the other hand, transition curvature increases when exchange constant decreases. Although on-track isolated pulse width of a differentiated signal is not affected much by transition curvature, the off-track isolated pulse width is larger when transition curvature is larger.