ORIENTATION OF CHLOROPHYLL-DOPED NEMATIC LIQUID CRYSTAL BY MAGNETIC FIELD
DOI: 10.18083/LCAppl.2025.3.17
The orientation effects of pure and chlorophyll b (Chl. b)-doped nematic 5CB using the Faraday method and the Fredericksz transition have been investigated. To analyze these effects, the volume diamagnetic anisotropy ΔΧ, which was considered as an orientation parameter, was determined. This parameter is absent in the symmetric state of the system above the temperature TNI (transition of nematic phase into isotropic liquid) and it appears during spontaneous symmetry breaking, when the system passes to an asymmetric nematic state. A discrepancy between ΔΧ(H) dependences with increasing of magnetic field H was found. The discrepancy is caused by an increase in ΔΧLC of the liquid crystal due to the contribution ΔΧChl of Chl. b due to the additional current induced in the porphyrin ring by the magnetic field. A decrease in the threshold field for the chlorophyll-doped nematic 5CB Hth = 3.18 kOe as compared with the value Hth = 3.55 kOe of pure 5CB was obtained. It is associated with an increase in ΔΧChl due to the introduction of a chlorophyll porphyrin ring into the liquid crystal. Orientational transitions during minimization of free energy in a layer of pure and chlorophyll-doped nematic 5CB are considered.