Fig. 1: T = 0 phase diagram of the classical Hamiltonian \({{{{{{{\mathcal{H}}}}}}}}\) as a function of the single-ion anisotropy D and the external field h, for \({J}_{2}/|{J}_{1} |=2/(1+\sqrt{5})\) and Δ = 2.6.
From: CP2 skyrmions and skyrmion crystals in realistic quantum magnets

The two insets show the phases for small-D and large-D, respectively. The solid (dashed) lines indicate 1st- (2nd-) order phase transitions.