Emergent Disorder Screening in Ag-Zn Co-doped Magnetic MnTe Thermoelectrics: Carrier Concentration-Stabilized Mobility for Enhanced Electronic Transport

Abstract

MnTe is intrinsically attractive as a magnetic thermoelectric material due to its large Seebeck coefficient and inherent magnetic ordering; however, its practical thermoelectric performance is limited by poor electrical conductivity arising from intrinsically low carrier concentration and restricted carrier mobility. Prior studies have shown that Zn doping suppresses spin-disorder scattering by reducing magnetic moments, thereby enhancing carrier mobility, yet achieving a simultaneous increase in carrier concentration while preserving these favourable transport characteristics remains a significant challenge. Here, Ag co-doping is introduced into Zn-doped MnTe to substantially increase hole concentration while maintaining reduced magnetic moments. Although Ag-Zn co-doping introduces additional disorder, the increased carrier concentration screens impurity scattering, enabling the retention of carrier mobility and a concomitant enhancement of the electronic power factor. The increased carrier density also reshapes carrier-phonon interactions, promoting acoustic-phonon-dominated scattering at elevated temperatures and concomitantly suppressing lattice thermal conductivity. The combined optimization of electrical and thermal transport properties leads to a pronounced enhancement of thermoelectric performance, yielding a peak figure of merit, zT ~ 1.0 at 873 K. These results establish carrier concentration-driven disorder screening as a robust and general strategy for achieving disorder-tolerant transport and enhanced thermoelectric performance in magnetic semiconductors.