Noncollinear antiferromagnetic structure and commensurate—incommensurate transition of DyNiC 2 studied by magnetization measurement, neutron diffraction and 161Dy Mössbauer spectroscopy

Abstract

Magnetic properties of powdered and single-crystalline DyNiC 2 are investigated by means of magnetization measurement, neutron diffraction and 161Dy Mössbauer spectroscopy. DyNiC 2 is a noncollinear antiferromagnet below T N = 7.6 K. Below T t1 = 3.3 K there exists a commensurate antiferromagnetic phase described by a propagation vector of [ 1 2 1 2 0 ]. The Dy moments of 9.0μ B align with a direction defined by angles of θ = 49° from the c-axis and φ = 34° from the a-axis in the c-plane at 1.5 K. The commensurate and incommensurate phases coexist between T t1 and T t2 = 5.0 K. The incommensurate phase with a sinusoidal moment modulation is described by a propagation vector of [ 1 2 1 2 − δ 0 ] ( δ = 0.11) where the moments modulated with an amplitude of 9.2μ B align with a direction of θ = 45° and φ = 77° at 4.2 K. The assumption that the moment component along the a-axis decreases with increasing temperature between T t1 and T t2 gives satisfactory explanation about anomalous behaviors in temperature dependences of magnetic susceptibility and neutron reflection intensities.