论文标题
对称性减少对lnir $ _2 $ si $ _2 $ polymorphs的磁性特性的影响
Effect of symmetry reduction on the magnetic properties of LnIr$_2$Si$_2$ polymorphs
论文作者
论文摘要
许多四方化合物lnir $ _2 $ si $ _2 $（ln = lanthanoid）出现在两个多态相中，因此非常适合研究晶体结构与磁性性能之间的关系。我们已经从高温implux磁通量中种植了两种多晶型物的GDIR $ _2 $ si $ _2 $单晶，并研究了他们的各向异性磁性特性。具有Thcr $ _2 $ si $ _2 $结构（空间$ i4/mmm $）的较高对称形式在$ t _ {\ rm n} = 87 \，\ rm k $上订购抗fiferromagnet，而对于较低的对称化合物，cabe $ _2 $ ge $ _2 $ $ _2 $ $ _2 $ $ _2 $ t _ {\ rm n} = 12 \，\ rm k $。我们对单晶的磁性表征表明，对于两种化合物，磁矩在四方晶格的$ a-a $平面中对齐，但是对称的变化强烈影响矩方向的平面对齐。对于ln $ = $ er和ho，我们确认了太空群中的lnir $ _2 $ si $ _2 $的存在。这些较低的对称化合物的磁性特性与太空群$ i4/mmm $中的相关化合物有显着差异。
Many tetragonal compounds LnIr$_2$Si$_2$ (Ln = lanthanoid) occur in two polymorphous phases and are therefore well suited to study the relationship between crystal structure and magnetic properties. We have grown GdIr$_2$Si$_2$ single crystals of both polymorphs from a high-temperature indium flux and investigated their anisotropic magnetic properties. The higher symmetric form with the ThCr$_2$Si$_2$ structure (space group $I4/mmm$) orders antiferromagnetically at $T_{\rm N}=87\,\rm K$ while for the lower symmetric compound in the CaBe$_2$Ge$_2$ structure (space group $P4/nmm$) we determined a much lower \neel temperature $T_{\rm N}=12\,\rm K$. Our magnetic characterization of the single crystals reveals that for both compounds the magnetic moments are aligned in the $a-a$ plane of the tetragonal lattice, but that the change of the symmetry strongly effects the inplane alignment of the moment orientation. For Ln$=$Er and Ho, we confirmed the existence of LnIr$_2$Si$_2$ in the space group $P4/nmm$. The magnetic properties of these lower symmetric compounds are in remarkable difference to their related compounds in the space group $I4/mmm$.
