Abstract
We study both analytically and numerically the edge of two-dimensional ferromagnets with Dzyaloshinskii–Moriya (DM) interactions, considering both chiral magnets and magnets with interface-induced DM interactions. We show that in the field-polarized (FP) ferromagnetic phase magnon states exist which are bound to the edge, and we calculate their spectra within a continuum field theory. Upon lowering an external magnetic field, these bound magnons condense at a finite momentum and the edge becomes locally unstable. Micromagnetic simulations demonstrate that this edge instability triggers the creation of a helical phase which penetrates the FP state within the bulk. A subsequent increase of the magnetic field allows to create skyrmions close to the edge in a controlled manner.
Highlights
The presence of the Dzyaloshinskii-Moriya (DM) interaction in ferromagnets favours a spatial twist of the magnetization leading to modulated magnetic textures like helices and skyrmion lattices, i.e., closely packed arrangements of single skyrmions
Co-Zn-Mn alloys with the chiral space group P4132 were shown to possess the typical phase diagram of other chiral magnets but with a skyrmion lattice phase stabilized at room temperature[14]
The atomic crystal of chiral magnets explicitly breaks inversion symmetry so that the DM interaction is even present in bulk samples
Summary
The presence of the Dzyaloshinskii-Moriya (DM) interaction in ferromagnets favours a spatial twist of the magnetization leading to modulated magnetic textures like helices and skyrmion lattices, i.e., closely packed arrangements of single skyrmions. Certain magnetic multilayers comprising magnetic Co and Fe atoms show stable skyrmion configurations at room temperatures[15,16,17] In all these systems, the DM interaction arises due to a lack of inversion symmetry. We demonstrate that with the help of a certain magnetic field protocol skyrmions can be created in a controlled manner at the edge of a magnetic monolayer by exploiting a local edge instability of the field-polarized state, see Fig. 1. For this purpose, we investigate the edge of a single magnetic layer with DM interaction that is polarized by a perpendicular magnetic field.
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