Temperature-dependent perpendicular anisotropy and Gilbert damping of L10- FePd films: Role of noble-metal buffer layers

The moderate bulk perpendicular magnetic anisotropy (PMA, Ku≈1MJ/m3) and low Gilbert damping (α < 0.01) make L10-FePd a promising candidate for energy-efficient and nonvolatile spintronic devices with large areal densities (down to 5-nm pitch sizes or even lower). Existing applications subject spintronic devices to a wide range of operating temperatures (e.g., -55 to 150 °C). To better address the technological viability of FePd for spintronic applications, it is of utmost importance to evaluate the material performance of L10-FePd (e.g., anisotropy strength and Gilbert damping) at elevated temperatures. In this work, we systematically investigate the effect of buffer layers (Cr/Pt, Cr/Ru, Cr/Rh, Cr/Ir, and Ir) on the PMA and Gilbert damping of L10-FePd from room temperature (RT, 25 °C) to 150 °C using the time-resolved magneto-optical Kerr effect metrology. It is found that the effective anisotropy field (Hk,eff) of FePd decreases with the testing temperature (Ttest) and the ratio of Hk,eff(150 °C)/Hk,eff(25 °C) is positively correlated to the degree of L10 phase ordering. The Gilbert damping of L10-FePd either increases with Ttest or stays nearly constant over the Ttest range. We attribute the temperature dependence of Gilbert damping to the spin diffusion length of the metallic buffer layer (λ), presumably through the spin pumping effect. Results of this work provide guidance to tailor L10-FePd properties through buffer layer engineering for applications in spintronic devices over wide operating temperature ranges.