Tailoring non-collinear magnetism by misfit dislocation lines

TL;DR

This study demonstrates how misfit dislocation lines in a strained Fe film on Ir(111) influence local magnetic structures, including spin spirals and skyrmions, through strain-dependent exchange interactions.

Contribution

It reveals the strain-dependent magnetic behavior caused by dislocation lines and models the variation of spin spiral periods via effective exchange coupling changes.

Findings

Spin spirals with periods from 3 to 10 nm depend on local strain.

Skyrmions are observed only in specific dislocation line regions.

The magnetic properties are linked to variations in exchange interactions due to strain.

Abstract

The large epitaxial stress induced by the misfit between a triple atomic layer Fe film and an Ir(111) substrate is relieved by the formation of a dense dislocation line network. Spin-polarized scanning tunneling microscopy (SP-STM) investigations show that the strain is locally varying within the Fe film and that this variation affects the magnetic state of the system. Two types of dislocation line regions can be distinguished and both exhibit spin spirals with strain-dependent periods (ranging from 3 nm to 10 nm). Using a simple micromagnetic model, we attribute the changes of the period of the spin spirals to variations of the effective exchange coupling in the magnetic film. This assumption is supported by the observed dependence of the saturation magnetic field on the spin spiral period. Moreover, magnetic skyrmions appear in an external magnetic field only in one type of dislocation line area, which we impute to the different pinning properties of the dislocation lines.