Diffusion critique des neutrons dans les systèmes magnétiques localisés et itinérants.
Mardi 07/11/2006, 14:30
LLB - Bât 563 p15 (Grande Salle), CEA-Saclay
Critical magnetic fluctuations in localized and itinerant magnets have been studied by means of bulk methods and polarized neutron scattering. The effect of the dynamical and spontaneous chirality on the critical behavior is discussed. Results of spin fluctuations in the critical temperature range of the localized magnet EuS are presented. The inclined field geometry in SANS experiments is used to induce the chirality in EuS. Results of the chiral fluctuations in the itinerant magnet MnSi are discussed. I will show that the incommensurate magnetic peaks evolve with increasing temperature into diffuse scattering that is mainly concentrated in rings around the nuclear Bragg peaks. In the presence of a magnetic field, I will discuss the wave vector and spin reorientation phase transitions at low temperatures.