Multiple-q states and skyrmion lattice of the triangular-lattice   Heisenberg antiferromagnet under magnetic fields
  Ordering of the frustrated classical Heisenberg model on the triangular-lattice with an incommensurate spiral spin structure is studied under magnetic fields by means of a mean-field analysis and a Monte Carlo simulation. Several types of multiple-q states including the "skyrmion-lattice" state is observed in addition to the standard single-q state. In contrast to the Dzyaloshinskii-Moriya interaction driven system, the present model allows both skyrmions and anti-skyrmions, together with a new thermodynamic phase where skyrmion and anti-skyrmion lattices form a domain state. 
Tsuyoshi Okubo, Sungki Chung, and Hikaru Kawamura
cond-mat.stat-mech cond-mat.mtrl-sci cond-mat.str-el