Thermal Conductance Analysis of the [FePt/h-BN/FePt] Interface

Heat-assisted magnetic recording (HAMR) requires a high thermal gradient in the recording media to suppress jitter noises. The FePt-(h-BN) granular film has been proposed as a promising medium due to the formation of columnar grains in the film structure. It is also expected to have a low in-plane (IP) thermal conductivity for enhanced thermal gradient. Accurate measurements of the thermal conductance of nanometer-scale thin films remain challenging, but multilayer structures can provide an important platform for studying the thermal transport in nanocomposite materials. Here, we report on the fabrication and thermal characterization of [h-BN/L<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1_{\mathbf {0}}$ </tex-math></inline-formula>-FePt] <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times {N}$ </tex-math></inline-formula> multilayers, where h-BN nanosheets (2.5 nm thick) and L<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1_{\mathbf {0}}$ </tex-math></inline-formula>-FePt layers (6.5 nm thick) alternate periodically. Differential <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\omega $ </tex-math></inline-formula> measurements reveal an ultralow effective thermal conductivity of 0.60 ± 0.05 W<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> m−1 K−1 across the multilayer films and a low thermal boundary conductance (TBC) of 67.9 ± 6.6 MW<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> m−2 K−1 for the [FePt/h-BN(2.5 nm)/FePt] interface at room temperature. The weak van der Waals bonding at the h-BN/FePt interface is considered the primary contributor to its high thermal resistance. This work can advance the understanding of thermal transport across the 2-D-material/metal contacts and provide valuable insights for the design of HAMR media with thermally isolated FePt grains.