Effects Of Ion Doping On The Crystal Structure And Magnetic Properties Of PrMnO₃

As a kind of strongly related electronic material,the perovskite manganese oxide has a variety of physical phenomena such as colossal magnetoresistance effect,magnetic entropy effect,charge order,magnetic order and phase separation.Therefore,doping and modification of rare earth manganese oxides,and exploring its complex physical mechanism have important basic research value and application value.In this work,Pr_1-xLa_xMnO₃,Pr_1-xTb_xMnO₃ and PrMn_1-xFe_xO₃ samples are prepared by the sol-gel method.The effects of doping of La,Tb at A-site and Fe at B-site on the structure and magnetic properties of PrMnO3 have been systematically studied.The main experimental results are as follows:1.As the doping amount x of La increases,Pr_1-xLa_xMnO₃ undergoes orthorhombic O'phase to O phase and then R-3c structural phase transition.With the structural phase transition,the Mn-O-Mn bond angle changes from 156°to 162°,and then 164°.However,in the sample of the same structure phase,the Mn-O-Mn bond angle is almost unchanged,and the Mn-O octahedron distortion weakened.All samples undergo a paramagnetic-ferromagnetic phase transition.The competition between ferromagnetism and antiferromagnetism led to the appearance of a reentrant spin glass at low temperature.2.In Pr_1-xTb_xMnO₃ samples,no phase transition is observed as all samples remain O'phase,and the space group is Pbnm.In contrast to the La-doped samples,the Mn-O-Mn bond angle decreases first,and then tends to remain unchanged,and the Mn-O octahedron distortion enhances.The sample also undergoes a paramagnetic-ferromagnetic phase transition and a reentrant spin glass at low temperature.3.PrMn_1-xFe_xO₃ samples were kept in orthorhombic O'phase with low doping concentration.When x>0.3,the samples were orthorhombic O phase.The samples with low doping concentration showed a reentrant spin glass state at low temperature,while phase separation is observed in PrMn_0.7Fe_0.3O₃.High-concentration Fe doping destroys the low-temperature glassy state,but the magnetism at room temperature enhances significantly.