Magnetic And Electrical Transport Properties Of Double Perovskite La₃Mn₂TaO₉

As one of the symbolic magnetic materials, perovskite manganese oxide has broad application prospects and has been extensively studied both theoretically and experimentally. However, the existing researches primarily concerned the ABO3-type perovskite oxide with doping elements in A site or B site, rather than doping elements in both A site and B site.In this paper, nigger-brown La3Mn2TaO9were prepared with solid-phase reaction method. This process can be divided into three steps:grinding the mixture of La2O3(99.9%)、MnO2(99.9%) and Ta2O5(99.9%) for2hours, sintering the mixture at900℃for24hours with resistance furnace followed by grinding the mixture for2hours again, calcining the mixture at1440℃for24hours with high temperature muffle furnace followed by cooling to room temperature to get La3Mn2TaO9.The magnetic properties of sample indicate the ferromagnetism at lower temperature. The maximal magnetic entropy change is0.531J/Kg K at162K. According to the Arrott plot, we get the critical exponents are β=0.471±0.006, γ=1.099±0.030, δ=3.077±0.013and the Curie temperature is165±1K. Analyses of the scaling behavior indicate these critical exponents are accurate. These critical exponents are similar to mean-field model and the phase transition belongs to second-order continuous phase transition. These means that the interactions between the local magnetic moments are long-range correlated interaction. To get the electrical transport properties of sample, we measure the resistance from80K to300K. The resistivity changes from6.51×1010Ohm·m at80K to3.4X105Ohm·m at300K and the sample changes from insulating state to bad metallic state. The pattern of resistivity obeys the variable range hopping formula ρ=ρoexp(T/To)-1/4. After the linear fitting we get the Mott temperature To=3×108K.