Al掺杂NdFeO_3体系的晶体结构精修与磁特性研究

Study on the crystal structure refinement and magnetic properties of Al doped NdFeO_3 system

利用固相反应法制备了Al掺杂的NdFe1-xAlxO3系列化合物。通过X射线粉末衍射和结构精修分析发现,随着Al掺杂量的增加,样品晶胞参数变小,晶胞内Fe—O键长、Fe—O—Fe键角也发生了很大程度的改变,并且在a、b、c方向上存在不同的变化规律。Al掺杂导致样品结构上的改变对其磁学性质具有重要影响。磁测量结果表明,随着Al掺杂量的增加,由dzyaloshinsky-moriya(D-M)相互作用导致的宏观磁性逐渐减弱;由Nd离子磁晶格与Fe离子磁晶格耦合作用导致的体系自旋重取向相变温度向低温方向移动,样品的饱和磁化强度随着Al掺入浓度的增加呈减小趋势。表明Fe位非磁性元素Al的掺入,使得样品内部由D-M相互作用所引起的倾角反铁磁结构受到了明显的调制。

Al doped orthoferrites Nd Fe1-xAlxO3 was synthesized by solid state reaction. X-ray powder diffraction and the rietveld refinement results show a decrease in the lattice parameters as Al doping content x increasing. Higher Al doping level leads to significant change on Fe—O bond length as well as Fe—O—Fe bond angle in the unit cell,and such change shows different behaviors in the directions of a,b and c axis. Magnetic properties of the sample are significantly affected by the structure change of the sample,which was caused by Al doping. Magnetic measurement results indicate that weak ferromagnetic ordering resulted from Dzyaloshinsky-Moriya( D-M) interaction was reduced with the increasing Al doping content and the phase transition temperature of spin reorientation interaction owing to the interaction between Nd ion and Fe ions moves to lower temperature with higher Al doping level. Furthermore,magnetization of the sample was decreased along with the increasing Al-doping content,indicating that the canted antiferromagnetic structure is evidently modulated by the nonmagnetic Al-doping in Fe site.