Determining the anisotropy of bit patterned media for optimal performance

In conventional recording theory the transition width should be minimised by writing the transition at the location of the maximum head-field gradient, and this should be achieved by setting the coercivity equal to the head field at the location of maximum head field gradient (taking appropriate account of the variation of coercivity with field angle). In BPM it would therefore be natural to assume that the system could be optimised by setting the island switching field in a similar manner. In this paper we investigate what strategy of optimisation gives the minimum error rate, or maximum write-window, and whether different designs are more or less tolerant of anisotropy variations.