Coherent Neutron Scattering Study of the SmV → SmVI Transition in TBBA

Abstract

We have shown [1] by X-rays studies that an herring-bone local order exists in the hexagonal SmB_A phase or in the pseudo-hexagonal SmB_C (SmH) phase. When the studied compounds undergo a SmB_C → SmE_C transition, only four of the twelve diffuse spots characteristic of the herring-bone order become Bragg spots of the SmE_C phase. We have studied the dependence of the neutron scattered intensity, near the two kinds of diffuse spots of a single domain of the SmB_C phase of fully deuterated TBBA versus energy, scattering vector and temperature. We could not measure any energy broadening of the scattered intensity on a diffuse spot (the resolution of the spectrometer was of.16 mev). We followed the width and the intensity of the diffuse spots in the reciprocal space and from these measurements one can deduce the correlation length for the herring-bone order and the anisotropy of the rotation of TBBA molecules around their long axis in the SmBp phase. We compare our results with those deduced from incoherent neutron quasi elastic scattering [2] and NQR experiments [3].

Soumis au Journal de Physique.