Structural, magnetic and magnetocaloric properties of La0.8Ca0.2−xNaxMnO3 manganites (0≤x≤0.2)

Abstract

In this work, we report the effect of Na doping on the structural, magnetic and magnetocaloric properties in La0.8Ca0.2−xNaxMnO3 powder samples. Our polycristalline samples have been synthesized using the solid-state reaction method at high temperatures. The parent compound La0.8Ca0.2MnO3 crystallizes in the orthorhombic system with Pbnm space group. Na doping induces a structural transition from orthorhombic (Pbnm space group) to rhombohedral (R-3C space group) symmetry.Magnetization measurements versus temperature in a magnetic applied field of 50mT showed that all our investigated samples display a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature TC increases with Na content from 240K for x=0 to 330K for x=0.2. A large magnetocaloric effect has been observed in all samples, the maximum entropy change, │∆SM│max, shifts to smaller values with increasing Na content, from4.56J/kgK (x=0.05) to 2.3J/kgK (x=0.2) under a magnetic field change ∆µ0H of 2T.For the same applied magnetic field of 2T, the Relative Cooling Power (RCP) values are found to be constant around 91J/kg.