The pressure dependence of the electrical resistivity of vacancy-doped nanocrystalline manganites at up to 2GPa at room temperature was reported here for the first time. The nanocrystalline samples, with vacancy doping at La- or Mn-sites, were synthesized by using the sol–gel technique and the particle size was determined from the width of X-ray diffraction peaks. Pressure-dependent electrical resistivity measurements of a La-deficient system (La0.9Mn0.8Fe0.2OΔ) and a Mn-deficient system (La0.86Sr0.14Mn0.80Fe0.16OΔ) revealed a similar trend; with a sudden change in the resistivity at 0.3GPa. A further increase in pressure monotonically reduced the resistivity of the La-deficient system up to 1.6GPa, while the Mn-deficient system underwent another sudden change in resistivity at 0.78GPa. The behavior of the vacancy-doped systems was compared with a stoichiometric system, La0.8Sr0.2Mn0.8Fe0.2O3, which exhibited a similar phase transition at 0.52GPa. The cross-over of localized-electron to band magnetism could be clearly seen in low-temperature Mössbauer measurements.

High Pressure Electrical Resistivity Behaviour on Nanocrystalline Vacancy Doped Perovskite Manganites. M.Kumar, U.Chandra, G.Parthasarathy: Materials Letters, 2006, 60[17-18], 2066-8