Field-induced magnetic behavior in quasi-one-dimensional Ising-like antiferromagnet BaCo2V2O8 : a detailed single crystal neutron scattering study

Orateur : Béatrice GRENIER (SPSMS-INAC CEA Grenoble-UJF)

BaCo2V2O8 is a nice example of a quasi-one-dimensional quantum s pin system that can be described in terms of Tomonaga-Luttinger liquid physics. The magnetic field-temperature phase diagram was thoroughly established up to H = 12 T and down to T = 50 mK using single crystal neutron diffraction, providing a stringent test for theory. The major part of the seminar will concentrate on these results. The field-induced transition from the Néel phase to the incommensurate longitudinal spin density wave (LSDW) phase through a first-order transition will be presented in detail. Then, the critical exponents associated with the paramagnetic to ordered phase transitions will be focused on, and the determination of the magnetic order both in the Néel and in the LSDW phase will be described. The magnetic excitations have been measured in the Néel phase at H = 0 and T = 1.5 K using single crystal inelastic neutron scattering. These first results, that still deserve to be completed and interpreted, will be presented in the last part of the seminar.

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