Thesis presented May 30, 2006

Abstract:
This thesis is mainly concerned with the use of several polarized neutron scattering techniques for carrying high resolution diffraction and inelastic spectroscopy experiments. We describe exhaustively our neutron resonant spin-echo option ZETA, installed on the thermal triple-axis spectrometer CRG IN22 at Institut Laue Langevin. Through it, we study the nuclear structure and spin dynamics of several model systems. First, we are interested in the BaM₂(XO₄)₂ (M = Co, Ni; X = As, P) family which members are good prototypes of quasi-2D magnetic systems. The effect of magnetic ordering on lattice constants is revealed thanks to Larmor diffraction. Moreover, we show that the thermal evolution of optic magnon lifetime in BaNi₂(PO₄)₂ is strongly affected by the presence of defects in its structure. Then, we address the spin-chain and ladder compound Sr₁₄Cu₂₄O₄₁. We first focus on the study of the inelastic peak associated with the spin gap in the ladders spectrum and introduce a method capable of showing directly the degeneracy of the associated spin transition. We also evaluate its intrinsic linewidth and observe the effect of different charge ordering process on the material crystallographic structure. Ultimately, we adapt our instrumentation to perform time-resolved reflectometry experiments on a magnetic multilayer which can possess interesting properties for spintronics applications, through the so-called MIEZE technique.

Keywords:
Low-dimensional magnetic systems, Larmor diffraction, Neutron resonant spin-echo, Polarized neutrons, Neutron scattering, MIEZE

On-line thesis.