Field-induced evolution of magnetic ordering in the quantum spin system (CuBr)Sr₂Nb₃O₁₀ with a 1/3 magnetization plateau

Abstract

The field-induced evolution of the magnetic ordering in (CuBr)Sr₂Nb₃O₁₀ with a 1/3 magnetization plateau has been investigated by neutron diffraction under magnetic fields up to 10 T. With an increasing magnetic field, the zero-field helical antiferromagnetic (AFM) phase, AF1, with κ = [0 3/8 1/2] is replaced by a simple ferromagnetic phase with κ = [0 0 0], the formation of which is, however, retarded by the appearance of a second AFM, AF2, with κ = [0 1/3 ∼0.46]. Upon further increasing of the magnetic field, the AF2 phase disappears and only the ferromagnetic phase persists. The results clearly show that the magnetization plateau, induced by the competition between field-induced ferromagnetic, F, and AF2 phases, is coincidentally situated at M = 1/3 MS of the dc magnetization curve. The AF1 and AF2 phases have strongly differing magnetic propagation vectors and are therefore not directly related.