Magnetic and critical behavior studies of Ni2+-doped perovskite manganese oxides

Polycrystalline materials are critical to various applications, especially Room-temperature magnetic refrigeration technology, for which limited research has been conducted. In this study, polycrystalline La 0.8 Ca 0.2 Mn 1− x Ni x O 3 ( x = 0 and x = 0.3) samples were prepared using solid-phase reaction method. The influence of Ni doping on the phase of the preformed clusters of polycrystalline samples, magnetic entropy change, and critical behavior were studied. The results revealed that all the samples have cubic orthogonal structures. The two prepared samples exhibited the presence of preformed clusters at temperatures above the low-temperature magnetic transition temperature. The critical behavior parameters of both samples fit the tri-critical model best. The parent material exhibited a first-order to second-order phase transition. The Ni-doped sample exhibited a second-order transition. The maximum magnetic entropy changes of the La 0.8 Ca 0.2 Mn 1− x Ni x O 3 samples with x = 0 and x = 0.3 were determined to be 6.21 J kg −1 K −1 and 2.57 J kg −1 K −1 , respectively. Moreover, Ni doping decreased the magnetic entropy change to a level lower than that without doping.