Concentration and path-length dependence on the faraday rotation of magnetic fluids based on highly water-soluble fe3o4/paa nanoparticles synthesized by a high-temperature hydrolysis method

In this study, highly water-soluble Fe3O4/PAA (polyacrylic acid) nanoparticles (NPs) were synthesized by a high-temperature hydrolysis method. We report the first demonstration of the concentration and path-length dependence on the Faraday rotation (FR) for a magnetic fluid (MF) synthesized by this novel method. Experiments were performed in the DC regime (0-6 × 10-2 T) at room temperature. Measurements were carried out with 5-3.33 mg/ml and 1.18 mg/ml samples in cells (2, 5, 7 and 10) mm. The maximum rotation was recorded as 0.96° cm-1 for the 3.33 mg/ml concentration in the cell 10 mm. It was found that the magnetic fluid behaves with a distinctive phenomenon in different sized cells although its concentration was the same. The role of the different parameters on the FR was discussed via spatial limitations imposed by the cells and a premature saturation term. This work provides a new insight for FR investigations of MFs including highly water-soluble magnetic NPs.