Magnetically asymmetric interfaces in a (LaMnO$_3$)/(SrMnO$_3$) superlattice due to structural asymmetries

TL;DR

This study shows that structural asymmetries at interfaces in a LaMnO3/SrMnO3 superlattice cause magnetic asymmetries, with smoother interfaces supporting stronger ferromagnetism, highlighting the importance of atomic-scale roughness in oxide heterostructures.

Contribution

It reveals how structural roughness asymmetries at interfaces influence magnetic properties in complex oxide superlattices, a novel insight into interface engineering.

Findings

Enhanced magnetization at LaMnO3/SrMnO3 interfaces with smooth surfaces

Reduced ferromagnetic moments at rougher interfaces

Atomic-scale roughness destabilizes interfacial magnetic phases

Abstract

Polarized neutron reflectivity measurements of a ferromagnetic [(LaMnO$_3$)$_{11.8}$/(SrMnO$_3$)$_{4.4}$]$_6$ superlattice reveal a modulated magnetic structure with an enhanced magnetization at the interfaces where LaMnO$_3$ was deposited on SrMnO$_3$ (LMO/SMO). However, the opposite interfaces (SMO/LMO) are found to have a reduced ferromagnetic moment. The magnetic asymmetry arises from the difference in lateral structural roughness of the two interfaces observed via electron microscopy, with strong ferromagnetism present at the interfaces that are atomically smooth over tens of nanometers. This result demonstrates that atomic-scale roughness can destabilize interfacial phases in complex oxide heterostructures.