Effects of A-site cation disorder on structure and magnetocaloric properties in Y and Sr codoped La2∕3Ca1∕3MnO3 compounds

Structural and magnetocaloric properties for the perovskite manganite La2∕3−xYxCa1∕3−ySryMnO3 (x<0.2) have been studied. These compounds with the fixed A-site average ionic radii of 1.204A and Mn4+∕Mn3+ ratio were prepared by conventional solid-state reaction technique. The lattice parameters were obtained from refining x-ray diffraction diagrams preformed by Rietveld refinement method. The ferromagnetic ordering temperature TC increases abruptly owing to the increase in the competition between A-site size-disorder degree σ2 and double-exchange interaction resulting from Mn–O–Mn bond angle. Phase transition may be broadened due to the cation disordering at A-site. Sample with x=0.01 appears a large magnetic entropy ΔSM=3.3Jkg−1K−1 at the Curie temperature TC=274K, which may be used as a promising candidate for magnetic refrigerant near room temperature.