基于中子衍射的六方相Er_(1-x)Y_(x)MnO_(3)结构和磁学性能研究

Research on Structure and Magnetism of Hexagonal Er_(1-x)Y_(x)MnO_(3) Based on Neutron Diffraction

为研究六方钙钛矿氧化物中磁结构和稀土离子对磁性能的影响,以六方相ErMnO_(3)为母体,通过非磁性Y^(3+)离子对磁性稀土Er^(3+)离子的替代,利用X射线衍射、中子粉末衍射和磁性测量等表征手段,对六方化合物Er_(1-x)Y_(x)MnO_(3)的晶体结构和磁性进行系统研究。研究结果表明,Y^(3+)离子的掺杂并未引起晶体结构和磁结构的明显改变,同时发现六方晶体结构随温度的增加呈各向异性热膨胀,在ab面内膨胀而沿着c轴收缩。中子衍射实验结果表明,Er_(0.4)Y_(0.6)MnO_(3)样品的有序温度约为79 K,低温下系统的基态为反铁磁性,结构为Γ_(2)(P63c′m′)或Γ_(4)(P63′c′m)组态,与Er_(0.8)Y_(0.2)MnO_(3)相同。磁化测试结果表明,非磁性Y^(3+)离子掺杂量的增加削弱了磁化强度,2 K时磁性稀土离子Er^(3+)的自旋有序在外磁场下表现出铁磁信号。该研究阐明了Er_(1-x)Y_(x)MnO_(3)的磁性本质和稀土磁性调控特性,为其潜在应用提供了有力指导。

The Y-doped hexagonal perovskites ErMnO_(3)were synthesized and systematically investigated by X-ray diffraction,magnetometry and neutron powder diffraction,to elaborate the effect of the magnetic rare-earth ions on the magnetic Mn^(3+)sublattice as well as the magnetization property at low temperature.The results of both X-ray and neutron diffraction show that the crystal structure and magnetic structure are almost unaffected by Y^(3+)doping and maintain the undoped structure,implying a weak interaction between Er^(3+)and Mn^(3+).Meanwhile,an anisotropic thermal expansion behavior is disclosed for this hexagonal system,with a dilates while c contracts with the increase of temperature.The neutron diffraction data confirm that the ordering temperature is approximately 79 K for Er_(0.4)Y_(0.6)MnO_(3)sample below which Mn^(3+)sublattice order adopts aΓ_(2)(P63c′m′)orΓ_(4)(P63′c′m)ground state,identical to Er_(0.8)Y_(0.2)MnO_(3).The magnetometry measurements show that the spin of Er^(3+)is ordered and coupled with Mn^(3+)sublattice at low temperature,and the magnetization is weakened by the Y^(3+)doping.In conclusion,the result provides a deep insight into the magnetism of hexagonal ErMnO_(3)system,which offers a guidance for the potential application of this intriguing system.