Suspensions of magnetic nanoplatelets in external fieldsGregorin, Žiga (Avtor) Osterman, Natan (Mentor) ferrofluidsliquid magnetsmagnetic nanoplateletsdomainsdomain growth dynamicsdifferential dynamic microscopySAXSSANSstripe regimemicrofluidicsflowmagnetic field generation with flowFerrofluids are colloidal suspensions of magnetic nanoparticles in liquid media. Ferromagnetic ordering – with spontaneous magnetization in the absence of external fields – has been described in a system of permanently magnetised nanoplatelets suspended in n-butanol, concentrated enough to undergo the transition to the nematic phase. Such material shows magnetic domain structures analogous to those of solid-state ferromagnets. By optimization of fundamental interactions, the threshold concentration for the nematic ordering was significantly reduced. The optimized material allows reproducible and controllable analysis of domain structures and their formation dynamics, with domains forming on the time scale of seconds. Additionally, the effect of an external applied magnetic field on the fundamental nematic director fluctuations inside single domains has been studied with differential dynamic microscopy. The obtained results provide an estimation of the ferrofluid's spontaneous magnetization in the absence of external magnetic field. In an oscillating magnetic field, the platelets follow the magnetic field at low frequencies but tend to form stripes at high enough amplitudes and frequencies of the applied field. The stripe regime is examined optically and by X-ray and neutron scattering methods to obtain insight into the collective behaviour of the constituents in oscillating magnetic fields. The shape anisotropy of the platelets and the coupling between magnetic and optical properties lead to the effect of flow-induced ordering. We analyse the effect of flow on the generation of a non-zero net magnetisation, resulting in a measurable jump in the magnetic flux density outside of the capillary with flowing suspension and vice versa, the effect of an applied magnetic field on the flow velocity.20232023-06-16 07:15:02Doktorsko delo/naloga146910VisID: 131237COBISS_ID: 153537027sl