Synthesis of novel perovskite crystal structure phase of strontium doped rare earth manganites using sol gel method

In the present work, polycrystalline perovskites of R0.6Sr0.4MnO3 nanocomposites (R=La, Nd, or Sm) were synthesized using the sol-gel method in the presence of citric acid and polyethylene glycol as chelating and structure directing agents respectively. The synthesized gel was calcined at 800 °C for 5 h. The XRD revealed that the obtained nanocrystalline R0.6Sr0.4MnO3 is monoclinic crystal structure of space group (I2/a). TEM images showed that the prepared perovskites are homogeneous and uniform with particle sizes in a range 20-40 nm and the HR-TEM images and lattice fringes displayed the monoclinic structure. IV measurements showed that Nd0.6Sr0.4MnO3 has semiconducting properties at room temperature. With applying low magnetic field, a transition from semiconductor behavior to Ohmic resistivity was observed. The static resistance of Nd0.6Sr0.4MnO3 was calculated to be ~2.985 TΩ for semiconductor phase and the resistance increased 1000 times that gives rise to negative magnetoresistance (MR). The value of MR of Nd0.6Sr0.4MnO3 equals to 99.84%, which leads to the use of these materials in fabrication of magnetic devices in the industrial scale.