Magnetic and magnetocaloric properties of the first-order phase transition in Sm0.5+xSr0.5−xMnO3 compounds

In this work, we present a detailed study on the magnetic and the magnetocaloric properties of Sm 0.5+ x Sr 0.5− x MnO 3 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 ( T C ). We point out that all the samples undergo a first-order phase transition and exhibit a giant magnetocaloric effect. The magnetic entropy change (Δ S m ) of samples was calculated based on isothermal M ( H, T ) data. The maximum value of Δ S m (denoted as |Δ S max |) at around T C is found to be 2.6 − 8.9 J·kg −1 ·K −1 for Δ H = 30 kOe and depends on the value of x . We have also used the universal master curve method for the temperature dependences of Δ S m curves measured at different Δ H values, Δ S m ( T ,Δ H ), to distinguish the magnetic order in the samples. Interestingly, none of the Δ S m ( T ,Δ H ) curves for the samples follow the universal master curve, Δ S m ( T ,Δ H )/Δ S max versus θ = ( T −T C )/( T r − T C ). As a consequence, a breakdown in the universal behavior of Δ S m ( T ,Δ H )/Δ S max versus θ curve is another feature confirming a first-order phase-transition nature.