Spin-polarized scanning tunneling microscopy characteristics of skyrmionic spin structures exhibiting various topologies

Abstract

The correct identification of topological magnetic objects in experiments is an important issue. In the present work we report on the characterization of metastable skyrmionic spin structures with various topological charges ($Q=-3,-2,-1,0,+1,+2$) in the (Pt${}_{1-x}$Ir${}_x$)Fe/Pd(111) ultrathin magnetic film by performing spin-polarized scanning tunneling microscopy (SP-STM) calculations. We find that an out-of-plane magnetized tip already results in distinguished SP-STM contrasts for the different skyrmionic structures corresponding to their symmetries. Our work also establishes an understanding of the relationship between in-plane SP-STM contrasts and skyrmionic topologies through an investigation of the variation of the in-plane angle between the spins along the perimeter of the structures, which can be characterized by the local vorticity or linear density of the winding number. For spin structures exhibiting a uniform sign of the local vorticity throughout the whole skyrmionic area, we demonstrate that (i) $|Q|$ can be determined from a single SP-STM image taken by any in-plane magnetized tip, and (ii) an in-plane tip magnetization rotation provides the sign of $Q$ independently of the sign of the effective spin polarization in the tunnel junction. We also discuss cases where the local vorticity is changing sign. Finally, by increasing the Ir content of the PtIr overlayer, we find an appearing secondary outer ring in-plane SP-STM contrast that is indicative of attractive skyrmions or antiskyrmions.

9 pages manuscript, 8 figures

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Cited by in corpus (9)

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• Skyrmion-antiskyrmion droplets in a chiral ferromagnet
• Channeling Skyrmions: suppressing the skyrmion Hall effect in ferrimagnetic nanostripes
• Stability and magnetic properties of Fe double-layers on Ir (111)
• High-resolution combined tunneling electron charge and spin transport theory of Néel and Bloch skyrmions
• Theory of high-resolution tunneling spin transport on a magnetic skyrmion
• High-resolution tunneling spin transport characteristics of topologically distinct magnetic skyrmionic textures from theoretical calculations
• Fresnel Magnetic Imaging of Ultrasmall Skyrmion Lattices