Observation of complex magnetic behaviour in calcium doped neodymium manganites

Crystal structure and magnetic properties of polycrystalline Nd1-xCaxMnO3 (x = 0.0, 0.2, 0.3, 0.33, 0.4, 0.5, 0.6 and 0.8) manganites were investigated. The fine structural refinement using GSAS was found to undergo a transition from Pnma reflections to Pbnm reflections associated with the Ca substitution at x = 0.3. The magnetic ordering of these compounds witnessed distinct magnetic phases with variations of Ca substitution. Magnetic ordering of the parent compound, NdMnO3, was found as A-type antiferromagnetic (AFM) in accordance with the earlier reports, which progressively undergoes to canted A-type AFM for x = 0.2, pseudo CE-type AFM for the intermediate compositions, i.e. x = 0.3 to x = 0.5 and CE-type AFM for x > 0.5. The x = 0.2 compound exhibited ferromagnetic like (weak AFM) behaviour, and the critical exponent study reinforced the magnetic inhomogeneity of the compound. Hysteresis curves of all the compounds measured at different temperatures implied the presence of metamagnetic like transitions for the intermediate compositions (0.3 <= x <= 0.5). Relative cooling power (RCP) value of Nd0.8Ca0.2MnO3 was observed to be 900 J Kg(-1), at the higher magnetic field, making it a promising candidate for magnetic refrigeration applications.