Hall effect at a tunable metal-insulator transition

Using a rotating magnetic field, the Hall effect in three-dimensional amorphous GdxSi1-x has been measured in the critical regime of the metal-insulator transition for a constant total magnetic field. The Hall coefficient R-0 is negative, indicating electronlike conductivity, with a magnitude that increases with decreasing conductivity. R-0 diverges at the metal-insulator transition, and displays critical behavior with exponent -1 [R(0)similar to(H-H-C)(-1)]. This dependence is interpreted as a linear decrease in the density of mobile carriers nsimilar toR(0)(-1)similar toH-H-C, indicative of the dominant influence of interaction effects.