Monte Carlo studies of noncollinear magnetic phases in multiferroic Cu2OSeO3

Abstract

Monte Carlo simulations based on a first-principles-derived Hamiltonian are conducted to study the finite-temperature properties of chiral-lattice multiferroic insulator ${\mathrm{Cu}}_{2}{\mathrm{OSeO}}_{3}$. The use of this numerical technique (i) reveals basic features of the phase diagram as a function of temperature and external magnetic field, including the long-range helical phase at low temperature and zero magnetic field and the skyrmion lattice phase, in which skyrmions are arranged in a two-dimensional hexagonal lattice, and (ii) leads to the discovery of an overlooked vortex lattice phase in a narrow pocket of the phase diagram near the fluctuations' disordered-helical phase transition. The scheme also provides strong numerical evidence that the transition to a helical state in ${\mathrm{Cu}}_{2}{\mathrm{OSeO}}_{3}$ is of first order driven by critical fluctuations.