Ferromagnetism makes a doped semiconductor less shiny

TL;DR

Doping FeSi induces ferromagnetism and transforms its optical properties, making it less reflective in the ferromagnetic state, which is unusual among magnetic metals with low carrier density.

Contribution

This study demonstrates that carrier doping of FeSi creates a unique ferromagnetic half-metal with unprecedented optical behavior, contrasting with typical magnetic metals.

Findings

FeSi becomes less reflective when ferromagnetic

Semiconducting gap is eliminated in doped FeSi

Ferromagnetic state shows increased electron scattering

Abstract

Magnetic semiconductors have attracted interest because of the question of how a magnetic metal can be derived from a paramagnetic insulator. Here our approach is to carrier dope insulating FeSi and we show that the magnetic half-metal which emerges has unprecedented optical properties, unlike those of other low carrier density magnetic metals. All traces of the semiconducting gap of FeSi are obliterated and the material is unique in being less reflective in the ferromagnetic than in the paramagnetic state, corresponding to larger rather than smaller electron scattering in the ordered phase.