Magnetic instabilities in doped Fe$_2YZ$ full-Heusler thermoelectric compounds

TL;DR

This paper investigates magnetic instabilities in doped Fe$_2YZ$ Heusler compounds, revealing their negative impact on thermoelectric efficiency and providing guidelines to mitigate these effects for better material design.

Contribution

It uncovers the magnetic instability in doped Fe$_2YZ$ compounds and offers insights to avoid it, improving thermoelectric material development.

Findings

Magnetic instability reduces thermoelectric performance.

Guidelines to prevent magnetic instability.

Critique of the rigid band approximation.

Abstract

Thermoelectricity is a promising avenue for harvesting energy but large-scale applications are still hampered by the lack of highly-efficient low-cost materials. Recently, Fe$_2YZ$ Heusler compounds were predicted theoretically to be interesting candidates with large thermoelectric power factor. Here, we show that under doping conditions compatible with thermoelectric applications, these materials are prone to an unexpected magnetic instability detrimental to their thermoelectric performance. We rationalize the physics at the origin of this instability, provide guidelines for avoiding it and discuss its impact on the thermoelectric power factor. Doing so, we also point out the shortcomings of the rigid band approximation commonly used in high-throughput theoretical searches of new thermoelectrics.