Investigation of structural, magnetocaloric and electrical properties of La0.6Ca0.4−x Sr x MnO3 compounds

Abstract: The La0.6Ca0.4−x Sr x MnO3 (x=0, 0.2 and 0.4) samples have been elaborated by the solid-state method. X-ray powder diffraction shows that, for x=0, the sample crystallizes in orthorhombic phase, while, for x≥0.2 the structure becomes rhombohedral. The variation of magnetization as a function of temperature and applied magnetic field were carried out. All samples exhibit a PM-FM transition at the Curie temperature T C which increases with Sr2+ content. Magnetocaloric effect has been calculated in terms of isothermal magnetic entropy change. A large magnetocaloric effect has been observed in all samples, the maximum entropy change, , reaches the highest value of 6.70J/kgK under a magnetic field change of 5T with an RCP value of 285J/kg for La0.6Ca0.2Sr0.2MnO3 composition, which will be an interesting compound for application materials working as magnetic refrigerants near room temperature. The electrical transport behavior ρ(T) was also investigated. All the specimens undergo a metallic–semiconductor transition at the temperature T ρ . The ρ−T fit well with the phenomenological equation for conductivity under a percolation approach. [Copyright &y& Elsevier]