Meron-antimeron crystals in noncentrosymmetric itinerant magnets on a triangular lattice

Multiple-Q magnetic states often induce nontrivial topological spin textures, such as a skyrmion and a hedgehog. We theoretically investigate yet another multiple-Q state with topological defects, a meron-antimeron crystal (MAX), represented by a periodic array of the meron and antimeron with a half-integer skyrmion number. Performing simulated annealing for an effective spin model of noncentrosymmetric itinerant magnets on a triangular lattice, we show that rectangular-shaped and triangular-shaped MAXs are stabilized by the interplay between the biquadratic interaction arising from the spin-charge coupling and the Dzyaloshinskii-Moriya interaction arising from the spin-orbit coupling. We also discuss the effect of a magnetic field on the triangular MAX, where highly anisotropic responses against a field direction are found. In particular, we show that the triangular MAX turns into the skyrmion crystal for the fields along the y and z directions, while it is replaced by another chiral state for the field along the x direction. These results should inspire further experimental investigation of MAXs in itinerant magnets.

Automated summary

In this study, a theoretical investigation on a multiple-Q state with topological defects, called a meron-antimeron crystal (MAX), was conducted. Through simulated annealing, the stability of rectangular-shaped and triangular-shaped MAXs was demonstrated, along with the highly anisotropic responses to a magnetic field on the triangular MAX. These findings suggest the potential for further experimental exploration of MAXs in itinerant magnets.