Inelastic Neutron Scattering study of magnetic excitations in Triple Perovskites Ba3TRuIrO9 (T=Mg, Na and Zn)

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. Ba3MgRuIrO9 and Ba3NaRuIrO9 with mixed 4d (Ru) and 5d (Ir) moments present an interesting magnetic behavior with competing localized and itinerant magnetism. The magnetic susceptibility measurements show a magnetic transition of complex nature in Ba3MgRuIrO9 near 17 K arising from the localized nature of Ir/Ru magnetic moments with an average valence state of 5, whereas the localized Ir/Ru leads to a magnetic phase transition near 88 K in Ba3NaRuIrO9 with an average valence state of 5.5. The magnetic measurements on both the compounds show the presence of short-range ferromagnetic and long-range antiferromagnetic correlations. Further investigations using the neutron scattering measurements are compulsory to understand the localized Ir/Ru magnetism in Ba3MgRuIrO9 and Ba3NaRuIrO9. We have perfomed MARI express (RB2490265) on Ba3TRuIrO9 (T=Mg and Na) and we see magnetic excitations near 5 meV at 5K. We therefore propose to carry out a detail inelastic neutron scattering experiment to probe the magnetic excitations in these compounds. We propose to carry inelastic neutron scattering measurements on Ba3MgRuIrO9 and Ba3NaRuIrO9 using the MARI spectrometer. We will also measure Ba3ZnRuIrO9 for comparison, which orders ferromagnetically below 70 K.

具有化学式Ba₃MAA´O₉的6H钙钛矿（6H-perovskite）采用三重钙钛矿P63/mmc结构，由于该结构中A-A´间距更短，体系存在较强自旋轨道耦合（spin-orbit coupling），因此展现出颇具研究价值的磁学特性。
同时拥有4d（钌Ru）与5d（铱Ir）磁矩的Ba₃MgRuIrO₉和Ba₃NaRuIrO₉，其磁学行为兼具局域与巡游磁性的竞争效应，表现出独特的磁学特性。
磁化率（magnetic susceptibility）测试结果显示，平均价态为5的Ir/Ru磁矩局域化特征，使得Ba₃MgRuIrO₉在17 K附近出现性质复杂的磁相变；而平均价态为5.5的Ba₃NaRuIrO₉，则因Ir/Ru的局域化特性在88 K附近发生磁相变。
对这两种化合物的磁学测试均表明，体系中同时存在短程铁磁关联与长程反铁磁关联。为阐明Ba₃MgRuIrO₉与Ba₃NaRuIrO₉中Ir/Ru的局域磁学行为，亟需开展中子散射（neutron scattering）测试以开展进一步研究。
我们已针对Ba₃TRuIrO₉（T=Mg、Na）完成MARI快速实验（RB2490265），并在5 K下观测到5 meV附近的磁激发信号。因此，我们计划开展详细的非弹性中子散射（inelastic neutron scattering）实验，以探测这类化合物中的磁激发行为。
我们拟利用MARI谱仪，对Ba₃MgRuIrO₉与Ba₃NaRuIrO₉开展非弹性中子散射测试。同时，我们还将选取Ba₃ZnRuIrO₉作为对照样本进行测试，该材料会在70 K以下发生铁磁有序。