Giant Hall effect in granular Fe-SiO2 film

We have studied the resistivity, magnetoresistivity, and Hall resistivity for a few Fe-x(Si0(2))(1-x) granular films with Fe volume fraction x near the metal insulator transition threshold x(c). Both the ordinary Hall coefficient R-0 and the saturated extraordinary Hall resistivity rho(xys) were found to be enhanced by a factor of 10(4) when x approaches x(c). The largest measurable R-0 and rho(xys) at room temperature are about 10(-3) mu Omega cm/G and 250 mu Omega cm, respectively. By comparing with the Ni-rich NiFe-SiO2 system [A. B. Pakhomov, X. Yan, and B. Zhao, Appl. Phys. Lett. 67, 3497 (1995)], we found that the correlation between giant Hall effect and the resistivity with a -log T-like dependence is independent of the sign of the carrier. The feasibility of using such a system as a magnetic-field sensor is discussed. (C) 1997 American Institute of Physics.