Effect of Synthesis Techniques on Magneto-Transport Properties of Sodium-Doped Lanthanum Manganites

The effect of synthesis techniques on the structural, magnetic and magneto-transport properties of La1-x Na (x) MnO3 (x = 0.1 and 0.2) manganites has been investigated. The samples were prepared using two different techniques: sol-gel and poly vinyl alcohol (PVA) precursor methods. X-ray diffraction studies indicate a rhombohedrally distorted perovskite structure having R3-c space group. The particle sizes of all the samples are in the nanometer range. A ferromagnetic insulating (FMI) behavior has been observed for x = 0.10 manganite synthesized using sol-gel technique while poly vinyl alcohol precursor method shows ferromagnetic metallic (FMM) behavior. A large magnetoresistance has been observed at low temperature region for x = 0.10 sample prepared using sol-gel method. The room temperature magnetoresistance values of sol-gel-prepared samples are found to be higher than that compared to PVA precursor method. Finally, theoretical work on magnetocaloric properties of the samples at ferro to paramagnetic state is presented and the results are explained qualitatively.