Sources and Impact of Media Thermal Fluctuations in Heat-Assisted Magnetic Recording

Optical and thermal modeling is used to understand and quantify the contribution of different sources of temperature fluctuations in heat-assisted magnetic recording. The dominant sources of temperature fluctuations are spatial variations of the absorption in the recording layer and spatial variations of the underlayer effective thermal boundary resistance. They result in an increased transition jitter that is proportional to the amplitude of the source variations. Besides, the transition jitter amplitude strongly depends on the length scale of the source fluctuations: fluctuations with smaller periods lead to reduced jitter as a result of in-plane heat spreading within the medium layers. Temperature fluctuations are also proportional to the input laser power or to the average temperature gradient. Consequently, transition jitter arising from temperature fluctuations does not change with improved temperature gradients, in contrast to jitter resulting from Curie temperature distributions. Interface roughness is also investigated as it is a practical source of both optical absorption fluctuations and thermal property fluctuations. It is found to lead to sizeable jitter, whose amplitude is proportional to the roughness amplitude and reduces at small roughness wavelengths.