Néel and Brownian rotations in ferronematics

The magnetic Freedericksz transition was studied in the liquid crystal 4-(trans-4’-n-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT) doped with spherical magnetite nanoparticles of different size (4.2 nm, 11.4 nm, 31.4 nm and 112.7 nm). The volume concentration of magnetic particles in prepared ferronematics was ϕ=2×10−4. The obtained results showed that doping with the magnetic particles with size smaller than the Shliomis size increases the threshold of the magnetic Freedericksz transition while in the case of doping with the magnetic particles with size larger than the Shliomis size a decrease of the threshold of the magnetic Freedericksz transition was observed. In the case of doping with magnetic particles with size comparable with the Shliomis size, both Néel and Brownian rotations are present, however, the Brownian rotation is dominant.