Tunnel-type giant magnetoresistance in the granular perovskiteLa0.85Sr0.15MnO3

The grain-size-dependent transport properties in the granular perovskite ${\mathrm{La}}_{0.85}{\mathrm{Sr}}_{0.15}{\mathrm{MnO}}_3$ have been investigated. A giant magnetoresistance (GMR) effect, similar to that observed in granular transition metals, and a crystal intrinsic colossal magnetoresistance (CMR) have been simultaneously observed. With grain growth, the GMR effect gradually weakens and the intrinsic CMR effect becomes prominent in the present granular system. A resistivity formula originating from interfacial tunneling is obtained and the theoretical calculation is found to be in good agreement with our experimental results.