Investigation of Near-Field Radiative Heat Transfer of Multilayered Structures in Heat-Assisted Magnetic Recording

Near-field radiation effects in heat-assisted magnetic recording (HAMR) are important to contribute the heat transfer and hence the flying ability at the head disk interface. Investigation of the near-field heat transfer is essential to optimize the head disk interface. An equivalent simulation model of the head disk interface for studying the radiative heat transfer is provided in this paper. Both the head shape and the magnetic properties of material are considered in this paper. The dyadic Green's functions along with fluctuational electrodynamics as well as scatter matrix are employed to calculate the heat transfer at the head disk interface. The head is simplified as a nanosphere, while the disk is simplified as a semi-infinite multilayered structures, in which the thickness of all layers is in nanoscale. The results show that the near-field radiative heat transfer between the head and disk in HAMR can exceed the values predicted by the Planck blackbody calculation by a few orders of magnitude. The total power is found to exponentially increase when the distance between the head and disk decreases.

I. Introduction

To increase the areal density of hard disk drive (HDD), there are two effective methods, which are, to decrease the size of the grains and to lower the flying height. At present, the flying height has been lowered down to 1–2 nm, which is closed to the limitation. It is very difficult to increase the storage of HDD by further decreasing the flying height at present. There are also lots of challenges to achieve a high density by decreasing the grain-size. For example, when the size of grains decreases, new challenges caused by the superparamagnetic limit emerge, such as signal-to-noise ratio, thermal stability, writability tradeoff, and so on [1].