TUNNELING GIANT MAGNETORESISTANCE IN HETEROGENEOUS FE-SIO2 GRANULAR FILMS

Magnetic and transport properties are examined for heterogeneous Fe-Si O2 granular films prepared on glass substrates by rf sputteriug. The s uperparamagnetic nature and the tunneling giant magnetoresistance are observed in the films having Fe volume fractions smaller than 45%. The magnetization and magnetoresistance (MR) curves;Ire systematically an al?zed by the summation of two Langevin functions. The dependence of t he MR ratio on the Fe volume fraction is explained phenomenologically by the distance between the nearest-neighbor grain surfaces. The tempe rature dependence uf the MR ratio is also discussed.