First-principles investigation of structural, electronic, magnetic, mechanical and thermoelectric properties of PdFeMn_1−xSc_xSi Heusler alloys for thermo-spintronic applications

The integration of spin-polarized transport with efficient thermal energy conversion is a key objective in the development of next-generation multifunctional materials. In this work, first-principles calculations based on density functional theory are employed to investigate the tunable thermo-spintronic properties of the quaternary Heusler alloys PdFeMn1-xScxSi (x = 0, 0.25, 0.5, 0.75, and 1). The results confirm that all compounds are energetically, thermodynamically, and dynamically stable in the ferromagnetic configuration. Electronic structure analysis reveals half-metallic behavior for compositions with x <= 0.75, with a maximum spin-down band gap of about 0.18 eV, while the x = 1 compound exhibits a nearly half-metallic character. The total magnetic moment follows the Slater-Pauling rule, decreasing from 5 to 1 mu B with increasing Sc content. The Curie temperatures reach values as high as 851 K, indicating strong ferromagnetic stability. Furthermore, the investigated alloys exhibit promising thermoelectric performance, with Seebeck coefficients up to 407 mu V K-1 and low lattice thermal conductivity (similar to 0.49 W m(-1) K-1), with a maximum figure of merit of 0.88 at 300 K. These findings suggest that PdFeMn1-x ScxSi alloys are promising candidates for energy conversion and thermo-spintronic applications.