Zero-field skyrmionic states and in-field edge-skyrmions induced by boundary tuning

Abstract

When magnetic skyrmions are moved via currents, they do not strictly travel along the path of the current, instead their motion also gains a transverse component. This so-called skyrmion Hall effect can be detrimental in potential skyrmion devices because it drives skyrmions towards the edge of their hosting material where they face potential annihilation. Here we experimentally modify a skyrmion model system—an atomic Pd/Fe bilayer on Ir(111)—by decorating the film edge with ferromagnetic Co/Fe patches. Employing spin-polarized scanning tunneling microscopy, we demonstrate that this ferromagnetic rim prevents skyrmion annihilation at the film edge and stabilizes skyrmions and target states in zero field. Furthermore, in an external magnetic field the Co/Fe rim can give rise to skyrmions pinned to the film edge. Spin dynamics simulations reveal how a combination of different attractive and repulsive skyrmion-edge interactions can induce such an edge-pinning effect for skyrmions.

Finding metastable skyrmionic structures via a metaheuristic perturbation-driven neural network

“…To avoid effects coming from anticipated truncation, the coupling coefficients were considered up to 360 neighbors (within a distance of ∼ 7a from the reference site, where a = 3.84 Å is the experimental lattice parameter of the Ir host). In turn, the experimental value (0.4 meV/Fe [36]) is here assumed for the K U 1 uniaxial anisotropy constant. Concerning the Zeeman term in Eq.…”

Band filling effects on the emergence of magnetic skyrmions: Pd/Fe and Pd/Co bilayers on Ir(111)

“…As mentioned in the Introduction, recent investigations have shown that these intrinsic interactions can be experimentally modified by the application of external electric fields, strain, or by introducing high-spin orbit defects. Also, considering the demonstrated rigid-band-filling nature of the interactions, one can modify the J ij and D ij by shifting E F through, for instance, FeCo alloying [26,91]. Therefore, in this Section we consider initially the ab-initio parameters calculated for Pd/Co/Ir(111), which, after tuned, will be analyzed separately.…”

“…Examples of complex magnetism in atomically thin layers and at interfaces can be found by theoretical studies and measurements, e.g. the extensively investigated Pd/Fe bilayer on Ir(111) [12,25], as well as by decorat- * ivan.miranda@alumni.usp.br ing the film edge with Fe/Co spots [26]. In this system, the ground state is characterized by a spin-spiral configuration [27,28] and, when subjected to the action of an external perpendicular magnetic field [12,25,[29][30][31] (of ∼ 1 − 1.5 T and at low temperatures), the emergence of a skyrmion lattice can be observed.…”

Large interlayer Dzyaloshinskii-Moriya interactions across Ag-layers

“…In this work, we experimentally explore polycrystalline Co/Ag/Co stacks grown by magnetron sputtering. Hereby, Co belongs to the class of ferromagnets with dominating direct Heisenberg exchange interaction in the range of 0.7–2 × 10 −11 J/m (0.86–6 meV/bond) 33 , while Co/Ag/Co multilayers have been reported to only exhibit very weak antiferromagnetic RKKY interlayer exchange interactions (~−0.014 mJ/m 2 34 ). While Ag is also known for its large Rashba SOC (ξ Ag_Rashba ~ 0.11 eV 35 ), we were not able to find any data on interfacial DMI effects in Co/Ag superlattices.…”