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MA: Fachverband Magnetismus

MA 22: Surface Magnetism (Joint Session with O)

MA 22.8: Talk

Tuesday, March 21, 2017, 11:45–12:00, HSZ 401

Tailoring non-collinear magnetism by misfit dislocation lines — •Aurore Finco, Pin-Jui Hsu, André Kubetzka, Kirsten von Bergmann, and Roland Wiesendanger — University of Hamburg, Germany

Epitaxial ultrathin films can often exhibit reconstructed surfaces because of lattice mismatch with the substrate. Unlike in pseudomorphic films, the film structure thus induces symmetry breakings and has dramatic consequences on the magnetism. In the case of a three-layer-thick Fe ultrathin film on Ir(111), the large epitaxial strain is relieved by the formation of a dense dislocation lines network. Spin-polarized scanning tunneling microscopy investigations [1] reveal that the strain is locally varying within the Fe film and that this variation affects its non-collinear magnetic state. Two types of dislocation line regions are distinguished and show spin spirals with strain-dependent periods (between 3 nm and 10 nm). Using a simple micromagnetic model, we attribute the changes of the period of the 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 period of the zero field spin spiral. Moreover, magnetic skyrmions appear in an external magnetic field [2] only in one type of dislocation line areas, which we impute to their different pinning properties. Exploiting the strain relief in epitaxial ultrathin films hence appears to be an effective way to precisely and locally control magnetic states.

[1] A. Finco et al, Phys. Rev. B, in press.

[2] P.-J. Hsu et al, Nat. Nano., advance online, 2016.