Thermal conductivity of amorphous rare earth—transition metal thin films for magneto-optic recording

Abstract

The thermal conductivity of a magneto-optic recording layer of sputtered amorphous TbFeCoZr is measured, and the results correlated with the thin film microstructure. Thermal conductivity K⊥ perpendicular to the plane of the film is measured using a thermal comparator method, while thermal conductivity K ‖ parallel to the plane of the film is calculated from electrical conductivity using the Wiedemann-Franz conversion. K⊥ ∼ 7 W mK −1 for non-columnar dense films, while K ‖ ∼ 4 W mK −. For columnar, less dense films sputtered at higher pressures, K⊥ ∼ 4 W mK −1, while K ‖ ∼ 0.3 W mK −1. The lowering of K⊥ is probably due to the decrease in density, while the strong anisotropy in the thermal conductivity of the columnar material is due to the introduction of intercolumnar contacts perpendicular to the film plane. Magnetic coercivity also drops with increasing deposition pressure, owing in part to the introduction of voids and defects into the film.