Study of the ferrofluid structure in low magnetic field by polarized neutrons

Complete text of publication follows. The process of ordering ferrofluid (FF) structure in low magnetic field is studied. The sample was colloid of magnetic particles suspended in water at volume concentration 4%. The SANS experiment has been performed for two orientations of external magnetic field respective to the neutron velocity vector (a = 45 deg and 0 deg). The data has been analyzed over the whole range of the scattering pattern including the zone of the interference between scattered and thorough going neutron waves by using of optical theorem. This has allowed us to analyze a rather weak signal from magnetic subsystem and also to determine the particle size with accuracy better than 1%. From the dependence of the nuclear scattering contrast on a we have made a conclusion about particles ordering in structures similar to linear chains. Within the framework of proposed model of nuclear-magnetic form factor autocorrelator it was established that: 1) magnetic correlation radius is not exceed nuclear one, 2) magnetic contrast is not depend on a. FF-magnetization process was studied in the experiment on the Larmor precession of the polarization. (author)