Two-step transitions in noncollinear magnets

Abstract
A possibility for a two-step transition in noncollinear (twisted) magnets is studied by means of a renormalization-group (RG) technique near two dimensions. The microscopically derived RG equations allow a single transition governed by O(4) exponents but also two-step transitions with preliminary SO(2) or S2 ordering, depending on the microscopic Hamiltonian. A possible experimental signature of partial ordering is discussed.