ON THE ORIGIN OF THE GIANT HALL-EFFECT IN MAGNETIC GRANULAR METALS

A large, by a factor of similar to 10(3)-10(4), enhancement of Hall ef fect in cosputtered magnetic granular metals such as (NiFe)(x)-(SiO2)( 1-x) near the metal-insulator transition has been termed giant Hall ef fect (GHE). It is associated with a high resistivity which increases s lowly with decreasing temperature. We suggest that particle-size distr ibution which is singular at zero and quantum size effects may be resp onsible for these phenomena. From our scaling analysis of the relation s between resistivity, and the ordinary and extraordinary Hall effects , it follows that the extraordinary Hall resistivity rho(xys) scales w ith mobility as-rho(xys)proportional to mu(-gamma) with the exponent g amma approximate to 0.5, which is characteristically different from th e predictions of both the skew scattering (gamma approximate to 1) and the side jump (gamma approximate to 2) theories in homogeneous ferrom agnets.