Dynamic behavior of a nematic liquid crystal mixed with CoFe₂O₄ ferromagnetic nanoparticles in a magnetic field

Abstract

The dynamic behavior of a mixture of 4-cyano-4′-pentylbiphenyl (5CB) with 1% CoFe2O4 nanoparticles was analyzed. Experimental data indicate a high stability of the nematic director in the mixture compared to a reference 5CB sample in the magnetic field. The ferrite nanoparticles agglomerate forming long chains as observed in polarized microscopy images. These chains have a very high influence on the magneto-optic effect of the cell. When the magnetic field is applied on the mixture, the chains tend to align with the field direction but, due to their large size, they remain oriented obliquely between the support plates. Thus, the nematic molecules anchored on their surface can not reorient with the field and only a small distortion angle of the liquid crystal molecular director is observed. A comparison with a previously developed theoretical model confirms this small deviation.

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 ].…”

Freedericksz Transitions in Twisted Ferronematics Subjected to Magnetic and Laser Field

“…These technologies are consequences of years of research into nanoparticle properties. In LC research fields, many studies have been performed on magnetic nanoparticle dispersions in nematic phases, called ferronematics [1][2][3][4][5][6][7][8][9][10][11][12]. There is also interest in other particles and their effect on the molecular order of the host [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31].…”

Intermittent time-set technique controlling the temperature of magnetic-hyperthermia-ablation for tumor therapy

“…The most popular magnetic nanoparticles in the biomedical eld are transition metal oxide, and some ferrites (BaFe 12 O 19 and CoFe 2 O 4 ). [13][14][15] Among them, iron oxide nanoparticles (Fe 2 O 3 or Fe 3 O 4 ) are the most commonly used because of their good biosafety. They can be delivered to the tumor through four different methods, 15 i.e.…”