Giant Hall effect in Co-SiO2 nanocomposites

Measurements of both the ordinary and extraordinary components of the Hall effect in co-sputtered granular magnetic CoSiO2 nanocomposites are presente d. The experiments were done in the temperature range 5-300 K, and fields u p to 7 T. Both components show a large enhancement when the metal volume fr action is reduced to the metal-insulator transition. However the enhancemen t of the ordinary Hall effect is much weaker than that of the extraordinary one. We discuss the implications of this observation for understanding of the giant Hall effect.