Investigation into the impact of grain-size and grain-size variation on system level error rates

Grain size and grain-size distributions are two parameters that play critical roles in the performance of magnetic recording media, in determining the densities that they support. Smaller magnetically isolated grains lead to less jitter noise, thereby leading to lower BER's and higher areal densities. Similarly, a smaller grain-size distribution indicates fewer larger and smaller grains again leading to less jitter noise and higher areal densities. In this paper, we study the impact of these two geometrical parameters on the system-level performance, holding all other magnetic parameters constant.

I. Introduction

The performance of magnetic recording media today is governed by many parameters, both magnetic and geometrical [1]–[2]. Two of the most critical parameters affecting the media's performance are the grain size (gs) and its distribution [3]. Larger grains tend to introduce more jitter into the readback signal as transitions necessarily follow the grain boundaries. Jitter is the main cause of errors in the magnetic recording channel, and hence larger grains result in more errors and thus support lower densities. In today's commercial media, the grain size is around 9nm with 6–7nm being achieved in research [1]. Grain-size distributions have a similar impact on the media's performance as larger distributions will include a larger percentage of large and small grains [4]. The larger grains will tend to increase the jitter and degrade the system's performance, while the smaller grains will lead to a larger proportion of thermally unstable grains.