FARADAY-ROTATION IN MAGNETIC GAMMA-FE2O3 SIO2 NANOCOMPOSITES/

Faraday rotation spectrum has been measured at room temperature in a m agnetic nanocomposite of gamma-Fe2O3/SiO2. The material consists of is olated gamma-Fe2O3 nanoparticles dispersed in a silica matrix, and it was prepared through a sol-gel method. The composite contains 18% of g amma-Fe2O3 in weight with an average particle size of 20 nm. It has a coercitivity of 30 Oe and an M-S of 6 emu/g. The specific Faraday rota tion spectrum exhibits a narrow peak centered around 765 nm, reaching a value of 110 degrees/cm and an absorption coefficient of 64 cm(-1). Faraday rotation versus applied held has also been measured, and a cyc le similar to the one described by the magnetization has been found. ( C) 1997 American Institute of Physics. [S0003-6951(97)02444-3].