XXZ-type interlayer exchange interaction in the bilayer triangular-lattice system as a source of multiple skyrmion phases

Abstract

We investigate the stability of the skyrmion crystal in a bilayer triangular-lattice system with the staggered Dzyaloshinskii–Moriya interaction. By focusing on the $XXZ$-type magnetic anisotropy for the interlayer exchange interaction, we construct the magnetic phase diagram in an external magnetic field based on the numerical simulated annealing. As a result, we find that the relative position of the skyrmion core in each layer is different depending on the easy-plane- and easy-axis-type interlayer exchange interactions. Furthermore, we find three additional skyrmion crystal phases with distinct spin and scalar spin chirality distributions. Our results indicate that the synthetic bilayer antiferromagnetic systems with the staggered DM interaction offer the multiple skyrmion crystal phases against an external magnetic field depending on the magnetic anisotropy parameter.