Write Errors in Bit-Patterned Media: The Importance of Parameter Distribution Tails

Bit-patterned media recording (BPMR) is a magnetic data storage solution where the medium is patterned into nanoscale islands, each representing one bit of data. Write errors can occur in BPMR, especially where islands have position, shape, or magnetic properties that are very different from the mean, i.e., those islands in the tails of any parameter probability density functions (PDFs). We have used a model of BPMR that incorporates variable shape parameter PDFs to study write errors. This shows that the precise shape of the tails of the distributions is critical in determining the error performance. We conclude that when characterizing samples of media for BPMR, it is not sufficient to assume a Gaussian distribution and determine the mean and standard deviation by fitting; the tails of parameter PDFs must be characterized precisely.