The magnetocaloric properties of manganite oxides La_0.7Sr_0.25Na_0.05Mn_1 − xAl_xO₃ (LSNMAl_x) synthesized by sol-gel method were studied in detail. X-ray diffraction analyses showed a single rhombohedral phase with the R3-c space group. The inhomogeneous magnetic compartment coupled with the core-shell behavior was used to explain the magnetic properties and the evolution of the paramagnetic-ferromagnetic transition of the materials. Using a phenomenological model, the maximum values of magnetic entropy change (ΔS_max) decreased from 4.92 J kg⁻¹ K for La_0.7Sr_0.25Na_0.05MnO₃ to 3.84 J kg⁻¹ K for La_0.7Sr_0.25Na_0.05Mn_0.95Al_0.05O₃ upon an applied magnetic field of μ₀H = 5 T, indicating an excellent quality of our samples as compared to many manganite oxides. The high quality of our samples was also checked by the large relative cooling power (RCP) which provides a good performance for industrial technologies in refrigeration devices.

中文翻译：

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La 0.7 Sr 0.25 Na 0.05 Mn 1-x Al x O 3的结构表征和磁相互作用

详细研究了通过溶胶-凝胶法合成的锰氧化物La _0.7 Sr _0.25 Na _0.05 Mn _{1-  x} Al _x O ₃（LSNMAl _x）的磁热性能。X射线衍射分析显示带有R3-c空间群的单个菱面体相。不均匀的磁性隔室与核-壳的行为相结合来解释材料的磁性和顺磁-铁磁转变的演变。使用现象学模型， La _0.7 Sr的磁熵变_最大值（ΔS _max）从4.92 J kg ^-1 K减小_0.25的Na _0.05 MnO的₃至3.84千克Ĵ ^-1  K中的La _0.7锶_0.25钠_0.05锰_0.95铝_0.05 ö ₃时所施加的磁场μ ₀ ħ  = 5 T，指示我们的样品的优异的品质相比，许多水锰矿氧化物。较大的相对冷却功率（RCP）也检验了我们样品的高质量，这为制冷设备的工业技术提供了良好的性能。