Experimental estimates of in-plane thermal conductivity in FePt-C granular thin film heat assisted magnetic recording media using a model layered system

Cross-plane thermal conductivity kth measurements of vertical stacks of FePt/C were used to estimate the in-plane thermal conductivity of Heat Assisted Magnetic Recording (HAMR) media that consist of columnar FePt grains segregated by thin C grain boundaries. FePt/C multilayers with varied repeat units and FePt layer thicknesses (chosen to represent HAMR media grain sizes) were measured using Frequency-Domain Thermoreflectance to determine kth in the direction normal to the layers. The data suggest that when FePt grains are less than 8 nm in diameter, the in-plane kth for HAMR media is below 1 W/m-K and the anisotropy of kth (cross-plane/in-plane) will exceed 10.