Ferromagnetism Enhancing Thermoelectric Transport Properties in Dilute Magnetic Semiconductor Ge1−xMnxTe
Mn-doped GeTe dilute magnetic semiconductors exhibit potential for mid-temperature thermoelectric applications, yet the mechanistic role of Mn in transport remains unresolved. This study characterizes the transport, magnetic, and lattice vibrational properties of Ge1−xMnxTe (x = 0–0.1) across 50–300 K. Mn incorporation reduces carrier concentration from ~1.2 × 10^21 cm−3 (x = 0) to ~4.5 × 10^20 cm−3 (x = 0.05) and amplifies electron scattering, yielding a two-fold increase in power factor to ~28 μW cm−1 K−2 at 300 K. Concurrently, Mn doping softens optical phonons and reduces phonon group velocity, suppressing lattice thermal conductivity to ~0.65 W m−1 K−1 at 300 K. Ferromagnetic ordering below ~120 K further depresses magnetic excitation phonon modes, contributing to the overall thermoelectric performance. These findings establish a dual electronic–thermal optimization pathway for GeTe-based dilute magnetic semiconductors.