Effect of A-site ionic disorder on magnetocaloric properties in large band width manganite systems

In this work, we explore the influence of A-site ionic disorder (σ2) on magnetocaloric properties in relatively larger bandwidth manganite systems like, well known La0.7Sr0.3MnO3 compound. For the study, three isoelectronic manganites with same A-site ionic radius (〈rA〉=1.24Å) i.e. La0.7Sr0.3MnO3(σ2=1.85×10−3), Pr0.7Sr0.14Ba0.16MnO3(σ2=1.17×10−2) and Nd0.7Sr0.07Ba0.23MnO3(σ2=1.66×10−2) samples have been prepared. Magnetic measurements reveal that, upon increasing σ2 from 1.85×10−3 to 1.66×10−2, ferromagnetic double exchange interaction diminishes and as a result, ferromagnetic ordering temperature (TC) decreases from 360 K to 100 K. Accordingly, the magnetic entropy change (−ΔSM) has also been found to decrease from 4.6 J/kg-K to 4.1 J/kg-K on the application of 70 kOe magnetic field. However, for σ2=1.66×10−2, the value of −ΔSM=5.7J/kg is relatively larger compared to the other two values of −ΔSM. Additionally, increased σ2 (1.85×10−3 to 1.66×10−2) broadens the peak of −ΔSM which results in the increase in relative cooling power (RCP) from 80 J/kg to 121 J/kg on application of 20 kOe magnetic field. Critical analysis has been performed to explain the enhancement in RCP with σ2 and the anomaly in −ΔSM for Pr0.7Sr0.14Ba0.16MnO3(σ2=1.17×10−2) compound.