ric acid were added to the above precursor solution in 1:1 mole ratio with respect to metal nitrates. The solution was magnetically stirred and heated on a thermal plate at $\sim$90 $^{o}$C until all the liquid evaporated out and black precursor powder was obtained. In order to get the well crystallized LSMO nanoparticles, the precursor powder was calcined at 800 $^{o}$C for 3 hrs in ambient atmosphere with heating rate of 2 $^{o}$C min$^{-1}$. To obtain the samples with different grain size, powder form of samples were pelletized in 5 mm diameter pellet under the pressure of $\sim$40 kg/cm$^{2}$, and pellets were sintered at 800 $^{o}$C (24 hr) and 850 $^{o}$C (72 hr). For the structural characterization, XRD diffraction pattern were recorded using the Rigaku Advance x-ray diffractometer using Cu K$\alpha$ radiation ($\lambda$= 1.5418 Å). The temperature dependent measurement of $\alpha$, $\rho$, and $\kappa$ were carried out using the home made setup.[@Patel; @resistivitysingh]\
Fig. 1 shows the XRD pattern of all the samples. To analyze the x-ray data, Rietveld refinement were performed using the FULLPROF software.[@rodriguez] From the refinement, goodness of fit $\chi$$^{2}$ was achieved to the 1.25, and the values of lattice parameters of the unit cell were *a* = 5.488(3) $\AA$ and *c* = 13.371(5) $\AA$. The refinement results (shown in the inset of Fig. 1) corresponding to rhombohedral structure described by R-3C space group confirms that sample is of single phase.[@radaelli]

![(Color online)XRD pattern of La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ sample. Rietveld refinement of XRD data (800 $^{o}$C, 3h) is shown in the inset of the figure.](LSMO.eps){width="45.00000%"}

The values of crystallite size (D) were calculated from the half-width (FWHM- Full Width Half Maximum) of most intense peak, using the Debye Scherrer formula, D = \[(k$\lambda$)/(B(*2$\theta$*).Cos $\theta$)\], where k is a constant (0.94), B(*2$\theta$*) is FWHM, and $\lambda$ is 1.5418 Å.[@warren] The estimated values of crystallite size were foun