Tunneling magnetoresistance and Hall effect of granular ferromagnetic metals

It is shown that two circumstances must be taken into account in order to d escribe the tunneling magnetoresistance and Hall effect in granular ferroma gnetic metals: 1) the size variance of the metallic granules and 2) the per colation character of the tunneling conductivity of the system, determining the optimal (temperature-dependent) size of the granules through which cur rent transport occurs. This complicates the dependences of the magnetoresis tance and Hall resistance of the system on its magnetization and temperatur e. (C) 1999 American Institute of Physics. [S0021-3640(99)01008-7].