Media Design and Orientation in Perpendicular Media

The variation of coercivity as a function of angle has been used to characterise the distribution of easy axis orientation in various media structures. This technique removes the effect of the demagnetising field (H_D) due to the zero value of the magnetisation (M) at the coercivity. The orientation distribution has been investigated via comparison with the Stoner-Wohlfarth model. We find that exchange coupled composite (ECC) media, which have the grains almost completely segregated, fit the simulation with a standard deviation of the orientation distribution of 5°. The calculation does not fit the experimental results for granular and continuous granular composite (CGC) media due to exchange coupling between the grains. In-plane and cross-section transmission electron microscopy (TEM) analysis have been carried out to investigate the effect of silica segregation of the grains on the exchange coupling.