Improvement of magnetocaloric properties over a large temperature range in 0.5La0.7Ca0.2Sr0.1MnO3/0.5La0.7Ca0.15Sr0.15MnO3 composite

Abstract

In the present research work, we investigate the magnetocaloric properties of a composite system by experiments and numerical calculations. The ability to adjust the magnetic entropy change in a large temperature range revealed to be possible by the mixture of both phases La0.7Ca0.2Sr0.1MnO3 and La0.7Ca0.15Sr0.15MnO3. Our composite 0.5La0.7Ca0.2Sr0.1MnO3/0.5La0.7Ca0.15Sr0.15MnO3 was synthesized using the solid–state reaction. Crystallographic structure and magnetocaloric properties were investigated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). Rietveld refinements of the X-ray diffraction patterns show that both samples are single phase and we have noticed a structural transition from orthorhombic structure with Pnma space group for La0.7Ca0.2Sr0.1MnO3 to rhombohedral structure with R-3C space group for La0.7Ca0.15Sr0.15MnO3. A second-order magnetic phase transition from ferromagnetic to paramagnetic state is observed and confirmed in terms of Landau theory. Therefore, two successive magnetic transitions in La0.7Ca0.2Sr0.1MnO3 and La0.7Ca0.15Sr0.15MnO3 resulting a nearly constant “table-like” magnetic-entropy change. Both peaks are partially overlapped with each other and induced an enhancement of the RCP in the composite when comparing with that of individual components. These results make that the proposed composite has substantial advantages for magnetic refrigeration.