Stroboscopic Small Angle Neutron Scattering Investigations of Microsecond Dynamics in Magnetic Nanomaterials

Ferrofluids and bio-ferrofluids: looking back and stepping forward

“…341 The stroboscopic small-angle neutron scattering technique consists in application of a cyclic perturbation to the sample by an oscillating magnetic field, allowing for extraction of the polarization-dependent scattering cross-sections as a time dependent response. 342,344…”

“…341 The analysis of time-dependent SANS data as a function of frequency, field and temperature allows (1) for proving the validity of the Langevin statistics describing the particle moment orientation, (2) for extraction of the effect of field-induced interparticle correlations, (3) for monitoring the slowing down of the dynamics of moment rotation with decreasing temperature, (4) for studying the effect of freezing of the solvent on the dynamics of the particle moments, and (5) for deciding between the possible relaxation mechanisms (Néel and Brownian). 342 Applying a continuous neutron flux allows for achieving the shortest time range of about 3 ms by the stroboscopic SANS technique in an oscillating magnetic field, 343,344 while the use of the pulsed beam (TISANE) technique extends the time resolution to the microsecond range. 341 The stroboscopic small-angle neutron scattering technique consists in application of a cyclic perturbation to the sample by an oscillating magnetic field, allowing for extraction of the polarization-dependent scattering cross-sections as a time dependent response.…”

“…341 The stroboscopic small-angle neutron scattering technique consists in application of a cyclic perturbation to the sample by an oscillating magnetic field, allowing for extraction of the polarization-dependent scattering cross-sections as a time dependent response. 342,344 In ferrofluids based on dielectric carriers, the formation of anisotropic aggregates of magnetic nanoparticles can be induced by direct current (dc) electric field, with a strong dependence on the field intensity, which was evidenced by SANS. 345,346 The anisotropic aggregates preferably orient in the direction of the applied electric field, giving rise to an electrorheological effect, analogous to the magnetic field induced viscosity increase.…”