HAMR Media Design in Optical and Thermal Aspects

In a heat-assisted magnetic recording (HAMR) system, the thermal performances of recording medium are very critical for recording density because the track density and bit density are dominated by thermal spot size in the cross-track direction and temperature gradient in the down-track direction. The optical intensity and its distribution generated by the near field optical transducer serve as a heat source to heat the medium. Therefore, the medium optical response to the transducer is also very important for the medium's thermal response. In this paper, based on the structure required by the magnetic performance, the effects of the medium structures on its optical and thermal performances are studied. The results show that a thinner interlayer (MgO layer) is beneficial to the medium's performance. However, the seed layer (NiTa layer) deteriorates the performance seriously. Small in-plane thermal conductivity (good isolation) of the granular recording layer is also very important for the thermal performance of the medium. However, the out-plane thermal conductivity is not very critical in certain ranges.