Critical Behavior Of The Perrovskite Eu_1-xSr_xMnO₄ Powders Prepared By Solid State Reaction

According to previous studies of ABO3 type perovskite materials, we know that the performance is special and very important, such as piezoelectric, high temperature superconducting, catalytic and magnetic cooling etc. Many groups have recently reported the structure and properties of perovskite materials.In this thesis, the perovskite manganese oxides Eu1-xSrxMnO3 (x=0.2 and 0.3) were prepared by the conventional solid-state reaction method. Stoichiometric amounts of the starting materials Eu2O3 (4N), SrCO3 (2N) and MnO2 (4N) were mixed, calcined and sintered in air condition, followed by slow cooling to room temperature. The structural characterization of the samples was examined by using X-ray diffraction (XRD). The powder XRD patterns revealed that these samples are a single phase perovskite structure without any impurity phase. All of diffraction peaks were assigned to the structure with a space group Pnma. The symmetry of the structure for x=0.3 is higher than x=0.2. The magnetic measurements in the temperature range 10 K-300 K were performed on a vibrating sample magnetometer. We have studied the critical behavior of the samples and determined the value of the Curie temperature (TC) and critical parametersβ,γandδ. These values are TC=52±1 K,β=0.57±0.02,γ=1.34±0.01,δ=2.78±0.01, and TC=56±1 K,β= 0.31±0.01,γ=0.67±0.02,δ=1.08±0.01 at x=0.2 and x=0.3, respectively. The critical parameters of x=0.2 sample is close to the mean-field theory. The maximum magnetic entropy change (|ΔSMmax|) and the relative cooling power of the samples are 3.174 mJ/g K,70.27 mJ/g and 2.382 mJ/g K,100.40 mJ/g corresponding with x=0.2 and x=0.3. These results show a large magnetic entropy change and the relative cooling power.