Abstract
We investigated the structural and magnetic properties of polycrystalline La0.67Sr0.33-x Ca (x) Mn0.75Fe0.25 O (3) (x = 0.00 and 0.17) samples. Rietveld refinement of X-ray powder diffraction (XRD) patterns shows that the samples adopt a rhombohedral structure with the space group. The average particle size of each sample was estimated from the most intense peak (104) of XRD pattern using Debye-Scherrer's formula. The average sizes are 73 and 82 nm. Static magnetic measurements, viz., hysteresis loops, field-cooled and zero field-cooled magnetization versus temperature curves of some samples carried out by BS1 and BS2 magnetometers in the temperature range of 400 to 5 K, clearly indicate the presence of a superparamagnetic (SPM) relaxation in the samples. Samples with x = 0.00 and x = 0.17 show an antiferromagnetic-paramagnetic (AFM-PM) transition at Neel temperature (T (N)) and a charge ordering transition, characterized by an extra peak (or shoulder) at T (CO). The magnetocrystalline anisotropy, average particle size, and its distribution were calculated from the analysis of the static magnetic data. The results are in good agreement with those obtained from XRD observations.