La_0.7Ca_0.3MnO₃ nanoparticle in an orthorhombic structure with space group of Pnma was prepared by a combination of the reactive milling method and annealing at 900 C for 1 h in air. The mean crystal size determined through the powder x-ray diffraction data is 182 nm. Based on the dependences of the resistivity and the magnetisation on temperature and applied magnetic field, the electrical-magnetic properties, the magnetoresistance and the magnetocaloric effects have been investigated. It shows La_0.7Ca_0.3MnO₃ nanoparticle undergoes a metal-insulator and a ferromagnetic-paramagnetic phase transitions at T_MI=252 K and T_C=253 K, respectively. The temperature dependences of resistivity of material in the absence and presence of 4 kOe in a range of 30–300 K were fitted to the phase segregation model. The magnetoresistance and the magnetocaloric effects related to the double-exchange interactions taking place around T_MI and T_C were observed, corresponding to the values of the magnetoresistance MR=9.29% and the maximum magnetic entropy change ∣ΔS_max∣=0.18 J/kg.K under an applied magnetic field of 4 kOe. Besides, the low field magnetoresistance value at low temperature region and the change of the specific heat of La_0.7Ca_0.3MnO₃ nanoparticle have also been concerned.

采用反应研磨法与空气中900℃退火1h相结合的方法制备了空间群为Pnma的正交结构La _0.7 Ca _0.3 MnO ₃纳米粒子。通过粉末 X 射线衍射数据确定的平均晶体尺寸为 182 nm。基于电阻率和磁化强度对温度和外加磁场的依赖性，研究了电磁特性、磁阻和磁热效应。它显示了 La _0.7 Ca _0.3 MnO ₃纳米颗粒在T _MI = 252 K 和T _C分别为 253 K。在 30-300 K 范围内，在不存在和存在 4 kOe 的情况下，材料电阻率的温度依赖性被拟合到相分离模型中。观察到与T _MI和T _C周围发生的双交换相互作用相关的磁阻和磁热效应，对应于磁阻值 MR=9.29% 和最大磁熵变 ∣Δ S _max ∣=0.18 J/ kg.K 在 4 kOe 的外加磁场下。此外，低温区的低场磁阻值和La _0.7 Ca _0.3 MnO ₃的比热变化 纳米粒子也受到关注。