Magnetic Studies on Gd-doped Perovskite Manganese Oxide Pr<sub>0.87</sub>Ca<sub>0.13</sub>MnO<sub>3</sub>

Perovskite manganese oxide doped with rare earth elements has great potential in magnetic refrigeration. Due to the prohibition of freon refrigerants and the greenhouse effect, the green and pollution-free magnetic refrigeration technology has been widely studied. Pr_{(0.87-<italic>x</italic>)}Gd_{<italic>x</italic>}Ca_0.13MnO₃(<italic>x</italic> = 0,0.05,0.10,0.15)series polycrystalline samples were produced by high temperature solid phase reaction method. The effects of doping amounts of Gd³⁺ on the structure, magnetic properties of parent Pr_0.87Ca_0.13MnO₃ samples were systematically investigated. The spatial point group of Pr_{(0.87-<italic>x</italic>)}Gd_{<italic>x</italic>}Ca_0.13MnO₃(<italic>x</italic> = 0, 0.05,0.10,0.15)series polycrystalline samples is the orthorhombic system Pnma, with the addition of Gd³⁺, lattice parameters (a, b, c) are gradually decreasing. This trend can be attributed to the partial substition of Gd³⁺ (ionic radius: 0.0938 nm) for Pr³⁺ (ionic radius: 0.099 nm), which has a smaller ionic radius. All samples in this series exhibit the typical characteristics of preformed cluster phase. The absolute values of the maximum magnetic entropy change (|？？| ) are 4.26962 J·kg^-1·K^-1(<italic>x</italic> =0)、4.89822 J·kg^-1·K^-1(<italic>x</italic> =0.05)、6.26870 J·kg^-1 ·K^-1(<italic>x</italic> = 0.1)、5.92600 J·kg^-1 ·K^-1(<italic>x</italic> = 0.15), respectively. The adiabatic temperatures (Δ<italic>T</italic>_{<italic>ad</italic>} ) were 3.76 K, 4.49 K, 6.52 K, and 6.39 K, respectively. All Arott display positive slopes, a characteristic that persists in the vicinity of the Curie temperature (<italic>T</italic>_C), indicating that the paramagneticferromagnetic transformation in all samples are second-order phase transitions. The results show that the critical behavior of Pr_0.87Ca_0.13MnO₃ and Pr_0.72Gd_0.15Ca_0.13MnO₃ samples is more similar to the mean field model, and the critical behavior of Pr_0.82Gd_0.05Ca_0.13MnO₃ samples is more similar to the 3D Heisenberg model. The phase transition critical behavior of Pr_0.77Gd_0.1Ca_0.13MnO₃ samples is more similar to the three-critical model.