A位平均离子尺寸对六方RMnO_3多铁化合物的结构和性能调控

Structure and Properties Modulation of RMnO_3 Multiferroic Materials by Average Ionic Radius at A-Site

实验研究了A位离子的化学内压对Ho1-xDyxMnO3(0≤x≤1)固溶体相结构物理性质的影响,发现掺杂稀土离子Dy3+所引起的内压力可使具有六方结构的HoMnO3向高压正交钙钛矿结构转变,形成六方相、六方相与高压正交相混相以及高压正交相3个区域。利用Rietveld方法,对Ho1-xDyxMnO3的X射线衍射数据进行结构精修,得到了六方相的晶格参数和晶胞体积随Dy3+含量的变化规律,此外还测量了磁化率和比热随温度的变化关系。研究结果表明,Dy3+对Ho3+的替代增强了稀土离子间的相互作用,使磁有序温度T2向高温方向移动,而Mn3+自旋重新取向温度TSR则呈现先减小后增加的趋势。

The effects of internal chemical pressure produced by A-site ionic radius were investigated for the Ho1-xDyxMnO3 system.It is found that the hexagonal HoMnO3 is gradually transformed to orthorhombic perovskite structure as reducing A-site ion size,forming three regions which contain pure hexagonal phase,mixture of hexagonal and orthorhombic phases and pure orthorhombic phase respectively.Using Rietveld method,the crystal structures were refined,and moreover,the correlations between lattice parameters and unit cell volume as a function of Dy3＋ ion content x were obtained.The properties of the temperature dependence of the magnetization and specific heat were also studied.It is suggested that Dy3＋-doping would increase the ordering temperature T2 of rare earth elements.