Skyrmions and multisublattice helical states in a frustrated chiral magnet

We showthat frustrated exchange interactions could stabilize chiral states in a chiral ferromagnet by considering the competition between ferromagnetic (FM) nearest-neighbor (NN) interaction and antiferromagnetic (AFM) next-nearest-neighbor (NNN) interaction. In the low-field regime, a multisublattice helical state is found, which is different from the normal one-sublattice helical states in a FM and the two-sublattice helical states in a two-sublattice AFM. As the field increases further, the skyrmion lattice is even stable with a much larger energy-preferable window than a system without frustration. We argue that the enlargement of the stability window of skyrmions is a consequence of the reduced effective exchange interaction caused by the frustration. As a byproduct, the hysteresis loop of the frustrated chiral system shrinks as the magnetization goes to zero and then opens up again, which is known as the wasp-waist hysteresis loop. The critical field that separates the narrow and wide part of the wasp-waist loop depends exponentially on the strength of NNN coupling. Our results provide physical insight into the chiral states in the magnetic systems with the coexistence of frustrated exchange and chiral interaction and might even prove important for novel devices, where the stability window of skyrmions is a key asset.