Designing heterostructures to control oxygen stoichiometry in helimagnetic perovskite strontium ferrite

TL;DR

This paper presents a method to stabilize and preserve the metallic, stoichiometric phase of SrFeO3 thin films by using a nanoscale insulator capping layer and ozone annealing, enabling better study of its helimagnetic properties.

Contribution

It introduces a novel stabilization technique for SrFeO3 thin films that prevents oxygen loss and maintains metallicity over weeks.

Findings

Oxygen loss causes degradation and phase crossover in SrFeO3.

Nanoscale band insulator capping combined with ozone anneal stabilizes SrFeO3.

Stable SrFeO3 films retain metallicity for several weeks.

Abstract

A large challenge in determining the physics of helimagnetic SrFeO3 is in stabilizing the stoichiometric chemical phase over long enough time scales to conduct extensive measurements. Degradation in SrFeO3 manifests mainly as a crossover from metallic to insulating behavior. Using a combination of electronic transport and density functional theory, we show that this degradation is dominated by oxygen loss, possibly on the order of one percent. We further demonstrate that high quality SrFeO3 thin films can be stabilized long-term by combining a nanoscale band insulator capping layer with an ex situ ozone anneal. We show that this produces a nearly-pristine cation sublattice and preserves metallicity for at least several weeks. These results establish a reliable pathway for producing chemically stable SrFeO3 thin films, enabling reproducible studies of its unusual helimagnetism.