Magnetic and magnetocaloric properties of the first-order phase transition in Sm0.5+x Sr0.5−x MnO3 compounds

Abstract

In this work, we present a detailed study on the magnetic and the magnetocaloric properties of Sm0.5+xSr0.5−xMnO3 compounds with x = 0 − 0.1, which were prepared by using a solid-state reaction method. The x-dependent magnetic, as well as magnetocaloric, properties, including the magnetic phase transition, have been studied. The increase in Sm/Sr ratio plays an important role in controlling the Curie temperature (TC). We point out that all the samples undergo a first-order phase transition and exhibit a giant magnetocaloric effect. The magnetic entropy change (ΔSm) of samples was calculated based on isothermal M(H, T) data. The maximum value of ΔSm (denoted as |ΔSmax|) at around TC is found to be 2.6 − 8.9 J·kg −1·K −1 for ΔH = 30 kOe and depends on the value of x. We have also used the universal master curve method for the temperature dependences of ΔSm curves measured at different ΔH values, ΔSm(T,ΔH), to distinguish the magnetic order in the samples. Interestingly, none of the ΔSm(T,ΔH) curves for the samples follow the universal master curve, ΔSm(T,ΔH)/ΔSmax versus θ = (T −TC)/(Tr−TC). As a consequence, a breakdown in the universal behavior of ΔSm(T,ΔH)/ΔSmax versus θ curve is another feature confirming a first-order phase-transition nature.