Inelastic Neutron Scattering study of magnetic excitations in triple perovskites Ba3RERuIrO9 (RE=Pr,Tb and Nd)

6H-perovskites with formula Ba3MAA´O9, which form in triple perovskite P63/mmc structure, display interesting magnetic properties on account of large spin-orbit coupling because of the shorter A-A´ distance in this structure. Among these the rare earth based triple perovskites Ba3PrRuIrO9, Ba3NdRuIrO9 and Ba3TbRuIrO9, which host 4f (RE), 4d (Ru) and 5d (Ir) moments and display fascinating magnetic properties with competing localized and itinerant magnetism, are of interest to us. Their magnetic susceptibility χ(T) data show magnetic phase transitions of antiferromagnetic nature near 3.4 K in Ba3PrRuIrO9, near 8 K in Ba3NdRuIrO9 and two phase transitions near 12.5 K and 5.5 K in Ba3TbRuIrO9. The χ(T) shows the complex nature of magnetic ordering in Ba3RERuIrO9 (RE = Pr, Nd and Tb) and reflects the presence of short-range ferromagnetic correlations along with the long-range antiferromagnetic correlations. Further investigations using the neutron scattering measurements are highly required to understand the magnetism and crystal field effect in Ba3RERuIrO9 (RE = Pr, Nd and Tb). We therefore propose to carry out inelastic neutron scattering experiment on Ba3RERuIrO9 (RE = Pr, Nd and Tb) using the MERLIN spectrometer to probe the magnetic excitations in these compounds.

化学式为Ba₃MAA′O₉的6H钙钛矿（6H-perovskite）采用三重钙钛矿P63/mmc空间群结构，由于该结构中A-A′间距更短，存在强自旋轨道耦合（spin-orbit coupling），因此展现出引人关注的磁学特性。其中，稀土基三重钙钛矿体系Ba₃PrRuIrO₉、Ba₃NdRuIrO₉与Ba₃TbRuIrO₉分别承载4f（稀土RE）、4d（Ru）及5d（Ir）磁矩，且呈现出局域磁与巡游磁相互竞争的极具特色的磁学行为，是本研究的重点关注对象。三者的磁化率χ(T)（magnetic susceptibility χ(T)）测试数据显示：Ba₃PrRuIrO₉在3.4 K附近出现反铁磁性磁相变，Ba₃NdRuIrO₉的反铁磁相变温度约为8 K，而Ba₃TbRuIrO₉则在12.5 K和5.5 K附近分别存在两次磁相变。上述磁化率结果反映出Ba₃RE RuIrO₉（RE=Pr、Nd、Tb）体系磁有序的复杂性，同时兼具短程铁磁关联与长程反铁磁关联。为深入阐明该体系的磁学行为与晶体场效应（crystal field effect），亟需借助中子散射（neutron scattering）技术开展进一步研究。因此，我们计划使用MERLIN光谱仪（MERLIN spectrometer）对Ba₃RE RuIrO₉（RE=Pr、Nd、Tb）开展非弹性中子散射实验（inelastic neutron scattering experiment），以探究该类化合物的磁激发特性。