Low-temperature resistivity minima in single-crystalline and ceramic LaSrMnO_3: Mesoscopic transport and intergranular tunneling Academic Article uri icon

abstract

  • A slight minimum in the zero-field resistivity of a single crystalline La 0.8 Sr 0.2 MnO 3 and shallow one for ceramic La 0.8 Sr 0.2 MnO 3 samples were observed at T∼ 4 K and at T∼ 25–30 K, respectively. The minimum for the ceramic shifts towards lower temperatures, flattens with increasing magnetic fields (H), and vanishes at some critical H. The above effects are accompanied by an appreciable negative magnetoresistance (MR). On the other hand, the minimum for the single-crystalline sample is almost field independent and the MR in the relevant temperature range is very small. Two different mechanisms were found to account for the results observed in the single crystal and the polycrystalline samples:(i) mesoscopic corrections to the bulk resistivity that include Coulomb interaction and weak localization and (ii) intergranular tunneling. The resistivity of the large-grain ceramic …

publication date

  • June 1, 2001