Dense skyrmion crystal stabilized through interfacial exchange coupling: Role of in-plane anisotropy

A Monte Carlo simulated-annealing algorithm was used to study the magnetic state in an in-plane helimagnet layer on triangular lattice that exchange couples to an underlayer with strong out-of-plane anisotropy. In the single helimagnet layer with in-plane anisotropy (K), the formation of labyrinthlike domains with local spin spirals, instead of parallel stripes, is favored, and these domains rapidly transform into dense skyrmion crystals with increasing interfacial exchange coupling (J '), equivalent to a virtual magnetic field, and finally evolve to an out-of-plane uniform state at large enoughJ '. Moreover, with increasingK, the skyrmion crystal state can vary from regular 6-nearest-neighboring circular skyrmion arrangement to irregular squeezed skyrmions with less than 6 nearest neighbors when the in-plane anisotropy energy is higher than the interfacial exchange energy as the skyrmion number is maximized. Finally, we demonstrated that the antiferromagnetic underlayer cannot induce skyrmions while the chirality inversion can be achieved on top of an out-of-plane magnetization underlayer with 180 degrees domain walls, supporting the experimental findings in FeGe thin film. This compelling advantage offers a fertile playground for exploring emergent phenomena that arise from interfacing magnetic skyrmions with additional functionalities.

Automated summary

The study investigated the magnetic state in an in-plane helimagnet layer on triangular lattice and found that the formation of labyrinthlike domains and dense skyrmion crystals occurs under certain conditions. The magnetic state can vary with increasing interfacial exchange coupling and in-plane anisotropy energy, demonstrating different behaviors such as irregular squeezed skyrmions and chiral inversion under specific circumstances.