Finite size effect on structural, morphological, magnetic, and magneto-optical properties of Fe₃O₄ based nanofluids

Present work deals to investigate the effect of finite-size particles pertaining to structural, morphological, magnetic, and magneto-optical behaviour. The structural, morphological, and magnetic investigation were done using XRD, Transmission electron microscopy (TEM) and vibration sample magnetometer (VSM) techniques, respectively. The particle size varies in the range of 7 to 15 nm. The dislocation density of atoms and strain varies with the particle size. A focused study on the magneto-optical tunability with intensity-induced refractive index was examined using novel in-house magneto-optical experimental technique at 25°C. The nonlinear refractive index coefficient is found to be of the order of 10⁻³. Also, size and concentration-dependent variation of nonlinear refractive index coefficient is observed. Significant optical multiple diffraction rings of the fluid under green laser illumination with different size and concentrations were observed. The sample with 1% concentration has the best limiting effect among the other two concentrations. Field-induced anisotropy and modulating magneto-optical response profiles in nanomagnetic fluid shows the potential application in magnetic sensors, magneto-optical switches, optical limiters, etc.