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

• La0.8Ca0.2−xNaxMnO3 are synthesized using the ceramic method at high temperatures.
• Na doping induces a structural transition from Pbnm to R-3C space group.
• TC increases with Na content from 240 K for x=0 to 330 K for x=0.2.
• RCP is constant around 91 J/kg for all compounds under 2 T.

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 50 mT showed that all our investigated samples display a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature TC increases with Na content from 240 K for x=0 to 330 K 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, from4.56 J/kg K (x=0.05) to 2.3 J/kg K (x=0.2) under a magnetic field change ∆µ0H of 2 T.For the same applied magnetic field of 2 T, the Relative Cooling Power (RCP) values are found to be constant around 91 J/kg.

Sodium doping induces an increase of TC from 240 K for x=0 to 330 K for x=0.2.Figure optionsDownload as PowerPoint slide