The temperature dependences of resistivity, magnetoresistance, and current-voltage (I-V) characteristics of grain boundaries in La0.6Pb0.4MnO3 thin films prepared using bicrystal SrTiO3 substrates were studied. Comparison of the resistances of the bridges, with and without grain boundaries, showed a contribution from disordered region near the grain boundary. This was taken into account for determination of the grain boundary characteristics. Analysis of the I-V characteristics showed that the transport through the grain boundary was dominated by multi-step inelastic tunneling as described by the Glazman and Matveev model. In addition a small contribution of elastic tunneling in agreement with the Simmons model was observed. Methodology for direct determination of the contribution responsible for magnetoresistance was developed and the results suggested that only elastic tunneling contributes to magnetoresistance. A small value of

the elastic tunneling contribution to the total current was found to be responsible for a small value of low field magnetoresistance.

Tunneling Characteristics and Resistivity Behavior of La0.6Pb0.4MnO3 Grain Boundaries. P.Chowdhury, S.K.Gupta, N.Padma, C.S.Viswanadham, S.Kumar, A.Singh, J.V.Yakhmi: Physical Review B, 2006, 73[10], 104437 (7pp)