Effect of A-site disorder of heavier rare earth ion on structural, magnetic and transport properties of lanthanum based chromium manganite perovskite system

In order to study the effect of A-site cation mismatch on the structural, magnetic and transport properties, a systematic investigation of La_0.6R_0.1Ca_0.3Mn_0.9Cr_0.1O₃ (A = La, Eu and Ho) has been undertaken. Rietveld analysis of powder x-ray diffraction data revealed that all the compounds crystallize in the orthorhombic symmetry with Pbnm space group. Temperature dependent magnetization studies showed that all our investigated compounds exhibit a paramagnetic-ferromagnetic transition at low temperature with Curie temperature (T_c) decreases with decrease in average A-site ionic radius (<r_A>). The materials show metal–semiconductor transition at low temperature and the values of metal–semiconductor transition temperature (T_MS) are found to be much lower than Curie temperatutre (T_c). It has been concluded that the conduction mechanism was dominated by small polaron hopping model in the high temperature paramagnetic semiconducting region.