Blocking phenomena studies on ferronematics

Liquid crystal doped with a small quantity of ferrofluid produces a ferronematic that can be oriented at low magnetic fields. In order for this orientation to occur the ferrofluid particles must be blocked at room temperature. It will be shown that this is possible only for the case of ferronematics doped with large (order of 10 nm) magnetic nanoparticles sizes. But when the ferrofluid added to the liquid crystal has smaller particles sizes it becomes superparamagnetic. Thus, it is observed that the Neel rotation of the smaller magnetic particles are facilitated by the liquid crystal environment, while for the larger ones the coupling to this environment is sufficient to raise the blocking temperature