We report the structural, magnetic, and magneto-caloric properties of as-synthesized (0.75)La_0.7Ca_0.3MnO₃/(0.25)La_0.84Sr_0.16MnO₃ nanocomposite material. The parent nanocrystalline samples synthesizes using pechini sol-gel route as well as sample's crystal structure was analyzed by Rietveld analysis of powder X-ray diffraction pattern. The nanocomposite sample showed two structural phases, which correspond to both the parent samples La_0.7Ca_0.3MnO₃ (Orthorhombic structure, Pbnm space group) and La_0.84Sr_0.16MnO₃ (Rhombohedral structure, $\text{R}\overline{3}\text{c}$ space group) respectively. The Williamson-Hall method was employed to calculate the crystallite size as well as strain in both parent samples. The values of crystallite size (D) and strain (ε) for La_0.7Ca_0.3MnO₃ are 65 nm and 0.0009 respectively and for La_0.84Sr_0.16MnO₃ are 37 nm and 0.0021. Homogeneity of the prepared compounds was confirmed with scanning electron microscopy (SEM) images. The temperature-dependent magnetization data displayed two successive transitions in the composite sample at 155 K and 255 K, which correspond to the parent samples. The respective maximum values of magnetic entropy change (−ΔS_M) were observed to be 1.9 Jkg⁻¹K⁻¹ and 3.03 Jkg⁻¹K⁻¹ at 5 T magnetic field for La_0.7Ca_0.3MnO₃ and La_0.84Sr_0.16MnO₃. To assess the ordering of the samples, Landau's analysis was carried out that reveals a good concordance with our experimental results. The broadened temperature range was found in the composite sample, consequently, the isothermal entropy change is reduced. An enhancement of 20%–25% of relative cooling capacity is noticed in the composite sample as compared to the parent samples.

我们报告了合成的 (0.75)La _0.7 Ca _0.3 MnO ₃ /(0.25)La _0.84 Sr _0.16 MnO ₃纳米复合材料的结构、磁性和磁热特性。母体纳米晶样品采用pechini溶胶-凝胶途径合成，样品的晶体结构通过粉末X射线衍射图的Rietveld分析进行分析。纳米复合材料样品显示出两个结构相，分别对应于母体样品 La _0.7 Ca _0.3 MnO ₃（正交结构，Pbnm 空间群）和 La _0.84 Sr _0.16 MnO ₃ （菱形结构， $\text{电阻}\overline{3}\text{C}$空间群）分别。Williamson-Hall 方法用于计算两个母体样品中的微晶尺寸和应变。La _0.7 Ca _0.3 MnO ₃的微晶尺寸(D)和应变(ε)值分别为65nm和0.0009，La _0.84 Sr _0.16 MnO _{3 的值为}37nm和0.0021。通过扫描电子显微镜 (SEM) 图像证实了制备的化合物的均匀性。温度相关磁化数据显示复合样品在 155 K 和 255 K 处的两个连续转变，这对应于母体样品。观察到磁熵变的各自最大值 (-ΔS _M ) 为 1.9 Jkg^-1 K ^-1和3.03 Jkg ^-1 K ^-1 在5 T磁场下对于La _0.7 Ca _0.3 MnO ₃和La _0.84 Sr _0.16 MnO ₃。为了评估样品的排序，Landau 的分析表明与我们的实验结果具有良好的一致性。在复合样品中发现加宽的温度范围，因此，等温熵变减小。与母体样品相比，复合样品中的相对冷却能力提高了 20%–25%。