Exchange-induced frustration in Fe/NiO multilayers

TL;DR

This study reveals how exchange interactions at Fe/NiO interfaces induce unique magnetic microstructures with small domain sizes, challenging traditional models based on anisotropy and dipolar forces.

Contribution

It demonstrates that interfacial exchange coupling causes unusual magnetic domain structures in Fe/NiO multilayers, supported by statistical analysis and micromagnetic modeling.

Findings

Magnetic domain area vs perimeter follows a power-law distribution.

Domain size cutoff is approximately 40 nm.

Interfacial exchange interactions dominate microstructure formation.

Abstract

Using spin-polarized low-energy electron microscopy to study magnetization in epitaxial layered systems, we found that the area vs perimeter relationship of magnetic domains in the top Fe layers of Fe/NiO/Fe(100) structures follows a power-law distribution, with very small magnetic domain cutoff radius (about 40 nm) and domain wall thickness. This unusual magnetic microstructure can be understood as resulting from the competition between antiferromagnetic and ferromagnetic exchange interactions at the Fe/NiO interfaces, rather than from mechanisms involving the anisotropy and dipolar forces that govern length scales in conventional magnetic domain structures. Statistical analysis of our measurements validates a micromagnetic model that accounts for this interfacial exchange coupling.