HAMR Media Jitter Relationships and Opportunities

Using the relationship of jitter with magnetic read width (MRW) and T50 for a large population of heads, measured jitter in heat-assisted magnetic recording (HAMR) is separated into written-in and remanent components. The subcomponent of written-in jitter related to the switching field distribution (SFD) is obtained by the relationship of jitter with the standard deviation of the write temperature
$\sigma _{\text {Tw}}$
. With increased laser power, it is primarily the remanent jitter that improves. As a function of write current, SFD-related jitter and noise due to erase after write increases, whereas thermal jitter improves, resulting in a minimum of jitter as a function of write current. This result agrees with our micromagnetic model. By improving the thermal gradient, SFD-related jitter is diminished, resulting in a higher optimum write current and lower optimum jitter. Thus, through head and media optimization, jitter potentially can be reduced to within about 0.3 nm of the limit set by media grain size.