Oxygen vacancy induced structural and domain size-controlled magnetic behavior of La0.67Ca0.33MnO3 perovskite

This article reports domain size-controlled magnetic behavior of La0.67Ca0.33MnO3 perovskite which was prepared by solid state reaction. The detail study includes structural information obtained with the help of Rietveld refinement of X-ray diffraction analysis. The structure was found as orthorhombic with the lattice parameters: a = 5.4850(4) angstrom, b = 5.4853(7) angstrom, c = 7.7583(9) angstrom belonging to the space group Pbnm. In addition, the crystallite size and micro-strain in the sample was found of the order of similar to 34 nm and 5.92 x 10(-3), respectively. The surface morphological study was also carried out with the help of FESEM with the EDAX analysis for verification of elemental composition which shows that the wt% of La, Ca, Mn and O elements were found as similar to 46.2, 3.8, 25.9 and 24.1, respectively, which is approximately equal to experimental values obtained by EDAX measurements. The SQUID was used to measure magnetic properties. The M-T measurements show that the reduction of departure between ZFC and FC curves with increasing magnetic field (B) is due to the overcome of external magnetic field to internal magnetic field of the sample. The M-H measurements were recorded showing the variation of magnetization as a function of B field at different temperatures (T = 5 K, 50 K, 100 K, 120 K, 200 K, and 300 K) within +/- 5 T. The absence of saturation at 300 K supports paramagnetic nature. The Delta M/Delta H under B field and variable T were also determined to study the domain size. The study of inverse susceptibility with temperature shows a straight line characteristic of the Curie-Weiss law with finding of Curie temperature as 212 K. Further dM/dT in FC mode shows a sharp peak at temperature 183 K which suggests that at this temperature thermal energy destroy the magnetic domain energy and magnetic moment aligns in random directions due to thermal energy.