Exchange-coupled <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>Fe</mml:mi></mml:math>-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>Pt</mml:mi

Heat-assisted magnetic recording (HAMR) is a promising high-density-data-storage technology whose intensive practical deployment requires a perfect balance of many factors, including device reliability, which is challenged by severe writing conditions. In this work, we propose HAMR media composed of $\mathrm{Fe}$-$\mathrm{Pt}$/$\mathrm{Ru}$/$\mathrm{Fe}$-$\mathrm{Pt}$ trilayer nanograins embedded in a carbon segregating matrix. When the $\mathrm{Ru}$ nonmagnetic spacer is thinner than 2 nm, the $\mathrm{Fe}$-$\mathrm{Pt}$ layers were found to be exchange-coupled and to exhibit different Curie temperatures, which is beneficial for lowering the HAMR writing temperature. Given the grain size of 17 nm, sufficient thermal stability was preserved according to the time dependence of coercivity analyzed with use of the Sharrock equation. The granular microstructure of $\mathrm{Fe}$-$\mathrm{Pt}$/$\mathrm{Ru}$/$\mathrm{Fe}$-$\mathrm{Pt}$ films with different $\mathrm{Ru}$ thicknesses was examined in detail, while their magnetic properties were interpreted by micromagnetic simulations distinguishing the properties of individual $\mathrm{Fe}$-$\mathrm{Pt}$ layers. Grain-size reduction, suppression of in-plane variants, and improvement of the degree of ${\mathrm{LI}}_{0}$ order in the top $\mathrm{Fe}$-$\mathrm{Pt}$ layer are further steps to optimize the developed exchange-coupled $\mathrm{Fe}$-$\mathrm{Pt}$/$\mathrm{Ru}$/$\mathrm{Fe}$-$\mathrm{Pt}$ nanogranular films that would open an avenue for tuning the HAMR media toward their ultimate performance.