Controlling electronic properties of hexagonal manganites through aliovalent doping and thermoatmospheric history

TL;DR

This study demonstrates how aliovalent doping and processing conditions can reversibly tune the electronic properties of hexagonal manganites, enabling their use in advanced electronic and energy devices.

Contribution

It provides a combined theoretical and experimental analysis of how doping and atmospheric history influence the semiconducting behavior of YMnO3, offering general guidelines for transition metal oxides.

Findings

Charge carrier concentration can be controlled via doping and defects.

Reversible switching between n-type and p-type conductivity achieved.

Method applicable to other transition metal oxides.

Abstract

The family of hexagonal manganites is intensively studied for its multiferroicity, magnetoelectric coupling, improper ferroelectricity, functional domain walls, and topology-related scaling behaviors. It is established that these physical properties are co-determined by the cation sublattices and that aliovalent doping can readily be leveraged to modify them. The doping, however, also impacts the anion defect chemistry and semiconducting properties, which makes the system highly sensitive to the synthesis and processing conditions. Here, we study the electronic properties of YMnO3 as function of aliovalent cation doping and thermoatmospheric history, combining density functional theory calculations with thermopower and thermogravimetric measurements. We show that the charge carrier concentration and transport properties can be controlled via both aliovalent cation dopants and anion defects, enabling reversible switching between n-type and p-type conductivity. This tunability is of importance for envisaged applications of hexagonal manganites in, e.g. next-generation capacitors and domain-wall nanoelectronics, or as catalysts or electrodes in fuel cells or electrolyzers. Furthermore, our approach is transferrable to other transition metal oxides, providing general guidelines for controlling their semiconducting properties.