Ordering effects on the thermal transport mechanisms in metallic alloys: Paper published in Scientific Reports – Congrats Ash!

Ash Giri’s work on the electron and phonon thermal transport mechanisms in ordered and disordered metallic alloys has recently appeared in Scientific Reports.  In this work, we show, via both experimental measurements and molecular dynamics simulations, that the thermal conductivity of an ordered metallic alloy (FePt) can have the same thermal conductivity as a disordered alloy at high temperatures.  This is due to a decreasing phonon thermal conductivity in the ordered alloy driven by three phonon scattering events.  This work has great implications for the thermal management involved in heat assisted magnetic recording applications.

Abstract

We report on the out-of-plane thermal conductivities of tetragonal L1₀FePt (001) easy-axis and cubic A1 FePt thin films via time-domain thermoreflectance over a temperature range from 133 K to 500 K. The out-of-plane thermal conductivity of the chemically ordered L1₀ phase with alternating Fe and Pt layers is ~23% greater than the thermal conductivity of the disordered A1 phase at room temperature and below. However, as temperature is increased above room temperature, the thermal conductivities of the two phases begin to converge. Molecular dynamics simulations on model FePt structures support our experimental findings and help shed more light into the relative vibrational thermal transport properties of the L1₀ and A1 phases. Furthermore, unlike the varying temperature trends in the thermal conductivities of the two phases, the electronic scattering rates in the out-of-plane direction of the two phases are similar for the temperature range studied in this work.

P.E.H. and A.G. appreciate support from the Air Force Office of Scientific Research, Grant No. FA9550-15-1-0079.