Magnetic and Optical Study of Nematic Liquid Crystal E7 Mixed Fe3O4 Ferrofluid

The magnetic and optical properties of suspension of ferrofluid (FF)-based spherical Fe
₃
O
₄
magnetic nanoparticles (MNPs) in E7 nematic liquid crystal (NLC) matrix have been investigated experimentally in an isotropic phase. The ferronematic liquid crystal (FNLC) mixture exhibits a uniform molecular interaction under an externally applied magnetic field as low as 2 kOe. While the pure NLC shows the expected positive birefringence behavior, the FNLC mixture shows an improvement in tunability with mainly a negative birefringence behavior. The magnetic measurements of samples, including the magnetization curve, hysteresis loop, and pertinent parameters, are carried out using a vibrating sample magnetometer (VSM). The optical properties of samples within the visible spectral range of 380-900 nm are investigated using spectroscopic ellipsometer (SE) device. The results and analysis of magnetic measurements using VSM device show initial magnetic susceptibility of 2.03 × 10
^-6
, 8.25 × 10
^-5
, 9.85 × 10
^-4
, and 3.38 × 10
^-2
for FLC0, FLC1, FLC2, and FLC3 samples, respectively. The analysis of SE data shows ordinary and extraordinary refractive indices n
_o
and n
_e
of FNLCs samples from 1.85 to 1.67 and from 1.73 to 1.40, respectively.