Discussion again of the magnetic and transport property of Ag-doped LaMnO3

Abstract Samples La 1− a Ag a MnO 3 (0.05⩽ a ⩽0.50) were sol–gel fabricated. A part of Ag was found to dissociate and run off the samples in sintering process when sintering temperature exceeds 700 °C, resulting in a composite of La 1− x Ag x MnO 3 and MnO 2 /Mn 2 O 3 . The magnetic and transport properties of the composite have been studied. The sample with the nominal composition La 0.7 Ag 0.3 MnO 3 was found to show the greatest magnetoresistance in the sample group. Detailed analysis on average Mn valence reveals a composite of (La 0.985 Ag 0.015 MnO 3 ) 0.776 [(MnO 2 ) 0.590 (Mn 2 O 3 ) 0.410 ] 0.224 . Its MR ratio at room temperature exceeds 24% under a field of 1.8 T. A conductivity leap has been observed around a =0.30. It suggests a kind of field-induced fluctuation in percolation in the samples investigated.