Enhanced magnetoresistance in sintered granular manganite/insulator systems

We report significant enhancements of magnetoresistance in granular (La0.67Ca0.33MnO3)χ/ (SrTiO3)1 - χ. The system exhibits a conduction threshold at χ = χc∼60%, around which magnetoresistance versus χ has a maximum. The composition χc at which maximum enhancement in magnetoresistance is observed is the same at high (around 5 T) and at low (a few hundred Oersted) fields. The enhancement is consistent with the disorder-driven amplification of spin-dependent transport at the structural boundaries of the mixture. © 1999 American Institute of Physics.