Insulator-to-metal transition and large thermoelectric effect in La$_{1-x}$Sr$_{x}$MnAsO

TL;DR

This study demonstrates that Sr doping in LaMnAsO induces an insulator-to-metal transition and results in a large thermoelectric effect, highlighting potential for thermoelectric applications.

Contribution

It reveals the insulator-to-metal transition mechanism via hole doping in LaMnAsO and reports high thermoelectric performance in doped samples.

Findings

Resistivity drops by five orders of magnitude with Sr doping.

Metallic behavior observed for x ≥ 0.08.

High Seebeck coefficient (~240 μV/K) in metallic samples.

Abstract

We report the Sr substitution effect in an antiferromagnetic insulator LaMnAsO. The Sr doping limit is $x\sim$ 0.10 under the synthesis conditions, as revealed by x-ray diffractions indicate. Upon Sr doping, the room-temperature resistivity drops by five orders of magnitude down to $\sim$0.01 $\Omega\cdot$cm, and the temperature dependence of resistivity shows essentially metallic behavior for $x\geq$0.08. Hall and Seebeck measurements confirm consistently that the insulator-to-metal transition is due to hole doping. Strikingly, the room-temperature Seebeck coefficient for the metallic samples is as high as $\sim240 \mu$V/K, making the system as a possible candidate for thermoelectric applications.