Observation of giant Hall effect in non-magnetic cermets

We study the Hall coefficient over a wide temperature range in co-sputtered Cu:SiO2 samples with metal volume fraction in the range of 0.45 less than or equal to x less than or equal to 0.8. With decreasing metal volume fract ion x, the samples change from metal to insulator and the Hall coefficient R increases drastically. A maximum has been observed at x = 0.51, which is similar to 700 times larger than that at x = 0.8. This enhancement far exce eds the factor of 20, which can be derived from the classical percolation ( finite size scaling) theory. Based on these observations, we conclude that the non-magnetic GHE arises most probably from quantum interference effects on the mesoscopic scale. (C) 2000 Elsevier Science B.V. All rights reserve d.