Effect of calcium doping on structural, magnetic and magneto-caloric properties of La0.55CaxSr0.45-xMnO3 manganites

Abstract

Effect of calcium (Ca) doping on structural, magnetic and magnetocaloric properties of calcium-strontium doped lanthanum manganite La0.55CaxSr0.45-xMnO3 (x = 0.00, 0.05, 0.1, 0.25) prepared by solid state reaction technique has been reported in this paper. Room temperature XRD measurements reveal rhombohedral structure for all the samples. Microstructural analysis have been done by the field emission scanning electron microscopy and elemental compositions are determined by energy dispersive X-ray diffractometer. It is observed that the lattice parameters as well as Mn-O-Mn bond angle are decreased with increasing Ca content which has changed the magnetic and magnetocaloric properties and tuned Curie temperature (TC) toward the room temperature. Magnetization measurement as a function of temperature reveals a reduction of magnetic saturation and decrease in Curie temperature from 354 K to 311 K with increase in Ca content from 0.00 to 0.25, respectively. A second order ferromagnetic to paramagnetic phase transition is noticed from their Arrots plots. The magnetocaloric effect is calculated in terms of entropy change and relative cooling power from the isothermal magnetization measurements around TC using Maxwell’s thermodynamic relations. The maximum entropy change and relative cooling power are observed to be decreased while TC shifted toward the room temperature with increase in Ca content in our studied polycrystalline manganite.