Magnetic Freedericksz transition in a ferronematic liquid crystal doped with spindle magnetic particles

Fréedericksz Transitions in 6CB Based Ferronematics—Effect of Magnetic Nanoparticles Size and Concentration

“…Such composite materials based on a nematic liquid crystal matrix with nanoscale magnetic admixture are known as ferronematics. Even a small amount of nanoparticles significantly influence magnetic [ 2 , 3 , 4 ], magneto-optical [ 5 ], morphological [ 6 ], dielectric [ 7 , 8 , 9 ], or electro-optical [ 8 , 9 ] properties. Dispersed nanoparticles enhance local short-range orientational order, order parameter, isotropic-nematic phase transition temperature, splay elastic constant [ 6 ], dielectric anisotropy [ 6 , 10 , 11 ], and dielectric permittivity [ 10 , 12 ], and decrease diffusion coefficient [ 11 ] and birefringence [ 13 ].…”

“…Moreover, properties relevant for display applications such as faster rising and falling time and lower threshold voltage [ 6 , 10 , 14 ] were observed. Most importantly, magnetic nanoparticles were found to be able to reduce a threshold magnetic field [ 2 , 3 , 4 ]. Lowering the threshold magnetic field, at which the response of liquid crystal molecules begins, has been the intention, since the first paper devoted to liquid crystals doped with magnetic particles was published in 1970 [ 15 ].…”

“…Lowering the threshold magnetic field, at which the response of liquid crystal molecules begins, has been the intention, since the first paper devoted to liquid crystals doped with magnetic particles was published in 1970 [ 15 ]. Since then, the composites consisting of various liquid crystals and magnetic nanoparticles have been studied experimentally [ 2 , 3 , 4 , 16 , 17 ] and theoretically [ 18 , 19 , 20 , 21 , 22 ]. Multiple experimental papers have reported [ 2 , 3 , 4 , 16 ] about decreasing in threshold magnetic field observed in composites of various liquid crystals and magnetic nanoparticles, but it was shown that increasing the threshold of magnetic fields can occur as well [ 17 ].…”

“…Since then, the composites consisting of various liquid crystals and magnetic nanoparticles have been studied experimentally [2][3][4]16,17] and theoretically [18][19][20][21][22]. Multiple experimental papers have reported [2][3][4]16] about decreasing in threshold magnetic field observed in composites of various liquid crystals and magnetic nanoparticles, but it was shown that increasing the threshold of magnetic fields can occur as well [17]. The influence of nanoparticles depends on their properties, which are related to material, size, shape, concentration, etc.…”

Smart Polymers for Microscale Machines

“…The Fréedericksz transition allow one to program the mesogen distribution with a sufficiently strong external field (i.e., magnetic and electric field). [ 142 ] When the field strength is higher than the threshold, the director will align itself to the field. Light‐induced Fréedericksz transition has also been reported to obtained mesogen programming with LCs doped with azobenzene moieties (e.g., azobenzene dye KD‐1).…”