Variations in optical transmittance with magnetic fields in nanosized FePt ferrofluid

Abstract

The optical transmittance increases with decreasing the concentration of FePt in both water-based and hexane-based ferrofluids. However, under an applied magnetic field H, the transmittance T increases with increasing H field. The variation in transmittance ΔT increases rapidly for samples in hexane at H=182 Oe. However, ΔT is very small for samples in distilled water. This can be explained due to the different aggregation ability of magnetic particles in ferrofluid. For the samples in hexane, its larger aggregation ability makes the magnetic particles easier to agglomerate and becomes much more chainlike elongated along the perpendicular magnetic field. Thus, it makes the area covered by the droplets per unit area in ferrofluid decrease and the ΔT increases with increasing the magnetic field. However, for samples in hexane, the optical properties may also be related with the Mie resonance. At H>60 Oe, the particle aggregation occurs and elongates more along the magnetic fields. This would cause the longitudinal plasmon resonance absorption to shift to a longer wavelength. Therefore, the absorption increases and the variation in transmittance ΔT decreases with increasing the incident wavelength.

Anomalous Decay in Short Time Response of Ternary Mixtures with Ferrofluid

“…Regarded from a broader perspective, the incomplete understanding of non-exponential relaxation remains one of the many unresolved problems in physics [43]. The ferrofluid problem, in particular, may comprise several complex components-the aggregation of magnetic particles [10], to mention but one possibility-each of which would challenge thorough understanding of the system.…”

“…These systems present induced magnetic birefringence under the action of magnetic field of various strengths and, for this reason, the optical transmittance of ferrofluids has attracted the interest of many groups [3][4][5][6][7][8][9][10][11]. These field-induced properties usually have special relaxation behavior that are particularly sensitive to the parameters characterizing the host medium.…”