Faraday rotation in magnetic gamma-Fe2O3/SiO2 nanocomposites

Faraday rotation spectrum has been measured at room temperature in a magnetic nanocomposite of gamma-Fe2O3/SiO2. The material consists of isolated gamma-Fe2O3 nanoparticles dispersed in a silica matrix, and it was prepared through a sol-gel method. The composite contains 18% of gamma-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 rotation 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 cycle similar to the one described by the magnetization has been found. (C) 1997 American Institute of Physics. [S0003-6951(97)02444-3].