Ferromagnetism Enhancing Thermoelectric Transport Properties in Dilute Magnetic Semiconductor Ge1−xMnxTe

• • Mn doping at x = 0.05 reduces carrier concentration from ~1.2 × 10^21 cm−3 to ~4.5 × 10^20 cm−3, optimizing the power factor to ~28 μW cm−1 K−2 at 300 K—a two-fold increment that directly enhances output power density in mid-temperature waste heat recovery. • • Lattice thermal conductivity is suppressed to ~0.65 W m−1 K−1 at 300 K via optical phonon softening and reduced phonon group velocity, enabling a projected zT improvement of ~40% over undoped GeTe at 300 K. • • Ferromagnetic ordering below ~120 K depresses magnetic excitation phonon modes, contributing an additional ~15% reduction in lattice thermal conductivity—a mechanism absent in non-magnetic dopants. • • The dual electronic–thermal optimization yields a peak zT of ~0.8 at 300 K for Ge0.95Mn0.05Te, demonstrating viability for near-room-temperature solid-state cooling where conventional Bi2Te3-based modules face cost and supply constraints.