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  Tsyrulin, N.; Batista, C.D.; Zapf, V.S.; Jaime, M.; Hansen, B.R.; Niedermayer, C.; Rule, K.C.; Habicht, K.; Prokes, K.; Kiefer, K.; Ressouche, E.; Paduan-Filho, A.; Kenzelmann, M.: Neutron study of the magnetism in NiCl₂ center dot 4SC(NH₂)₂. Journal of Physics: Condensed Matter 25 (2013), p. 216008/1-12

10.1088/0953-8984/25/21/216008
Open Access Version

Abstract:
We study the strongly anisotropic quasi-one-dimensional S = 1 quantum magnet NiCl2⋅4SC(NH2)2 using elastic and inelastic neutron scattering. We demonstrate that a magnetic field splits the excited doublet state and drives the lower doublet state to zero energy at a critical field Hc1. For Hc1 < H < Hc2, where Hc2 indicates the transition to a fully magnetized state, three-dimensional magnetic order is established with the AF moment perpendicular to the magnetic field. We mapped the temperature/magnetic field phase diagram, and we find that the total ordered magnetic moment reaches mtot = 2.1 μB at the field μ0H = 6 T and is thus close to the saturation value of the fully ordered moment. We study the magnetic spin dynamics in the fully magnetized state for H > Hc2, and we demonstrate the presence of an AF interaction between Ni2+ on the two interpenetrating sublattices. In the antiferromagnetically ordered phase, the spin-waves that develop from the lower-energy doublet are split into two modes. This is most likely the result of the presence of the AF interaction between the interpenetrating lattices.