Na-doped La0.7Ca0.3MnO3 compounds exhibiting a large magnetocaloric effect near room temperature

Abstract In this work, we have investigated the magnetic properties and the magnetocaloric effect of La 0.7−x Na x Ca 0.3 MnO 3 compounds, which were prepared by a conventional solid-state reaction technique. The Rietveld refinement results suggested that the samples are single phase belonging to an orthorhombic structure (space group Pnma ). Analyzing temperature dependence of magnetization M ( T ) revealed that the Curie temperature ( T C ) increases with increasing Na content ( x ). Their T C value is found to be 260–298 K for x =0.0–0.1, respectively. Base on M ( T ) data measured at different applied magnetic fields ( H ), temperature dependence of magnetic entropy change Δ S m ( T ) data for all the samples was calculated by using a phenomenological model. In the vicinity of T C, -Δ S m ( T ) curve reaches a maximum value (denoted as |Δ S max |), which gradually increases with increasing H . Under 12 kOe, the value of |Δ S max | is in a range of 1.47–5.19 J/kg K corresponding to the relative cooling power RCP=57.12–75.88 J/kg. Applied the universal master curve method for the magnetic entropy change, we concluded that Na-doped in La 0.7−x Na x Ca 0.3 MnO 3 compounds leads to modification the nature of the magnetic phase transition from the first- to the second-order.