Deficiency effects upon the physical properties of Pr_(0.8)Sr_(0.2)MnO_3 manganite oxide

摘要

The effects of deficiency in praseodymium and in strontium upon the magnetic and magneto-transport properties of lacunar Pr_(0.8)□_xSr_(0.2)MnO_3 and Pr_(0.8)Sr_(0.2-x)□_x MnO_3 oxides have been investigated. Our synthesized samples have been elaborated using the conventional solid state reaction at high temperature. Crystallographic studies show that all our samples are single phase and crystallize in the orthorhombic system with Pnma space group. The praseodymium deficient samples Pr_(0.8-x)□_xSr_(0.2)MnO_3 exhibit three different regimes in the resistivity variation as a function of praseodymium deficiency amount: (ⅰ) at low concentration (0 ≤ x ≤ 0.1), a semiconductor behaviour is observed in the whole temperature range, (ⅱ) at an intermediate amount (x = 0.15), a semiconductor-metallic transition is followed by a metallic-semiconductor one with decreasing temperature, and finally (ⅲ) at x = 0.2 and 0.25, a metallic behaviour is observed below T_C, whereas all the strontium deficient samples exhibit a semiconductor behaviour in the whole temperature range.