Superior bit error rate and jitter due to improved switching field distribution in exchange spring magnetic recording

TL;DR

This paper demonstrates that exchange spring magnetic media exhibit significantly reduced switching field distribution and jitter, leading to lower bit error rates, due to improved thermal stability and exchange coupling effects.

Contribution

It introduces a novel mechanism for reducing switching field distribution and shows how exchange spring media improve thermal stability and jitter performance over single-phase media.

Findings

Switching field distribution reduced by about 30%

Thermal stability leads to decreased transition jitter

Estimated jitter comparable to optimized heat-assisted media

Abstract

We report two effects that lead to a reduction of the switching field distribution in exchange spring media. The first effect relies on a subtle mechanism of the interplay between exchange coupling between soft and hard layers and anisotropy that allows significant reduction of the switching field distribution in exchange spring media. This effect reduces the switching field distribution by about 30% compared to single-phase media. A second effect is that due to the improved thermal stability of exchange spring media over single-phase media, thermal fluctuation leads to reduced fundamental transition jitter. The influence of this overall improved switching field distribution on the transition jitter in granular recording and the bit error rate in bit-patterned magnetic recording is discussed. The transition jitter in granular recording for a distribution of K1 values of 3% in the hard layer, taking into account thermal fluctuations during recording, is estimated to be a = 0.78 nm, which is similar to the best reported calculated jitter in optimized heat-assisted recording media.