Surface antiferromagnetism and incipient metal-insulator transition in strained manganite films

TL;DR

This study uses first-principles calculations to reveal surface-induced antiferromagnetism and a potential metal-insulator transition in strained La$_{1-x}$Sr$_{x}$MnO$_{3}$ films, highlighting surface effects on magnetic and electronic properties.

Contribution

It demonstrates that epitaxial compression induces antiferromagnetic surface layers and a pseudogap, providing new insights into surface magnetism and electronic transitions in manganite films.

Findings

Surface layers favor antiferromagnetic order under compression.

Surface exhibits a spectral pseudogap indicating a metal-insulator transition.

Large surface relaxations shift work function significantly.

Abstract

Using first-principles calculations, we show that the (001) surface of the ferromagnet La$_{1-x}$Sr$_{x}$MnO$_{3}$ under epitaxial compression favors antiferromagnetic ordering in the first few surface layers, coexisting with ferromagnetic bulk order. The change in magnetic order is accompanied by a marked surface-related spectral pseudogap, signaling a metal-insulator near-transition at the surface. All surfaces exhibit huge outward relaxations an rumpling of the MnO$_{2}$ and LaO surface planes, causing a distinct shift in work function. The AF phase is an extreme surface-assisted case of the combination of in-plane AF super-exchange and vertical FM double-exchange couplings that rules magnetism in manganites under in-plane compression.