Above room temperature magnetic entropy in non-stoichiometric manganese of La0.67Sr0.33MnO3 manganites

With an aim to improve the magnetocaloric effect above the room temperature for practical applications, La0.67Sr0.33MnO3 manganite with different manganese concentrations has been synthesized using a novel technique with oxalic acid as a fuel material. The X-ray photoelectron spectroscopy studies confirm the presence of mixed valence states of Mn3+ and Mn4+ with varying manganese content. Studies of the magnetic properties reveal that the samples undergo ferromagnetic to paramagnetic transitions well above room temperatures, i.e., around 383 K. The second order of magnetic phase transition has been confirmed from Arrott plots. The entropy change (ΔSM) over a wide temperature range was observed around magnetic transition temperature in all the samples which can be considered as a suitable material for magnetic refrigeration applications. A reduction in magnetic entropy in deficiency and excess of manganese samples has been attributed to the magnetic inhomogeneity.