Microwave absorption studies in ferrofluid composites

Magnetic field induced absorptions in ferrofluid composites containing aluminium particles have been studied in the microwave region (wavelength range 0.3 mm to 3 mm) using Fourier Transform Spectroscopy. The composites studied were in the form of thin films (≃ 30 µm thick) containing monolayers of aluminium particles dispersed in a decalin carrier ferrofluid of saturation magnetisation 500 G. Induced absorptions, as large as 60%, were observed in fields of 50 Oe in a composite containing 20% by volume of aluminium particles.