Comparative study of microscopic, spectroscopic and magneto-optic response of ferrofluids subjected to γ-radiation

Present work reports a comparative study of spectroscopic and magneto-optic properties of Fe₃O₄ based ferrofluids prepared with two different carrier fluid namely milli-Q-water and kerosene. The ferrofluids are labelled as FFW and FFK respectively. Both ferrofluids are subjected to γ-irradiation of dose: 2,635 Gy. Transmission electron microscopy and dynamic light scattering studies reveal that γ-photon interaction could lead to substantial growth of the dispersed nanoparticles of ferrofluids. In case of FFW, particle sizes are ∼9 nm (pristine) and ∼48 nm (irradiated) whereas, in FFK unirradiated particles of size ∼9 nm show growth to ∼18 nm after the irradiation. The role of different physical parameters (viz. viscosity, density) of carrier fluid on the growth process is considered in this regard. Viscosity of the carrier fluid is found noteworthy in the measurement of Faraday rotation response of the ferrofluids. In addition to low viscosity of water, irradiation induced particle growth as well as improved size distribution with larger particles leads to a comparatively larger enhancement of Faraday rotation of FFW than that of FFK. Consequently, as a result of γ-irradiation, Verdet constant is modified by ∼70 % in the former case and by ∼60 % in the latter case. (author)