空位破坏的自旋冰Ho2TiO5中的局域磁有序
Local magnetic order in vacancy-disrupted spin ice Ho2TiO5
AI总结：
本研究探究经典自旋冰Ho2Ti2O7转变为空位破坏的Ho2TiO5时的局域磁关联，发现后者保留伊辛各向异性但集体冰有序被破坏，拓扑不完整磁网络仍存局域冰规则倾向。
AI中文摘要：
我们研究经典烧绿石自旋冰Ho2Ti2O7转变为部分无序的填充型化合物Ho2TiO5时，局域磁关联的演化情况。通过实空间磁对分布函数、倒空间反演蒙特卡洛方法以及半极化中子粉末衍射方法分析中子散射测量结果，以关联平均晶体结构与局域磁关联。两种化合物均保留长程Fd-3m对称性，但Ho2TiO5中，该平均结构因Ho/Ti部分占据导致的Ho-O、Ti-O及O-O键长无序发生局域畸变。尽管存在这种无序，半极化中子粉末衍射显示，Ho磁矩仍保留局域<111>伊辛各向异性，并在四面体网络上形成自旋向内/自旋向外的构型。在0.3K时，实空间与倒空间分析表明Ho2Ti2O7呈现近乎理想的二进二出自旋冰态，95%的四面体满足冰规则，升温后则发生渐进热无序。在Ho2TiO5中，多数四面体磁结构不完整，因部分四面体顶点由非磁性Ti而非Ho占据；不过，占主导的不完整构型为二进一出和一进二出，若补充缺失的Ho自旋，这些构型在局域上仍符合冰规则。因此，单离子<111>伊辛各向异性全程保留，而集体冰有序则被强烈破坏：Ho2TiO5是一种空位破坏的自旋冰，在拓扑不完整的磁网络上仍存在局域冰规则倾向。
英文摘要：
We investigate how local magnetic correlations evolve when the classical pyrochlore spin-ice Ho2Ti2O7 is transformed into the partially disordered stuffed compound Ho2TiO5. Neutron scattering measurements were analyzed using real-space magnetic pair distribution function, reciprocal-space reverse Monte Carlo, and half-polarized neutron powder diffraction methods to connect the average crystal structure with local magnetic correlations. Both compounds retain long-range $Fd-3m symmetry, but in Ho2TiO5 this average structure distorts locally through Ho-O, Ti-O and O-O bond-length disorder associated with partial Ho/Ti occupancy. Despite this disorder, half-polarized neutron powder diffraction shows that the Ho moments retain local <111> rangle Ising anisotropy and form spin-in/spin-out configurations on the tetrahedral network. In Ho2Ti2O7, real- and reciprocal-space analyses reveal a nearly ideal two-in/two-out spin-ice state at 0.3K, with 95% of tetrahedra satisfying the ice rule, followed by progressive thermal disordering on warming. In Ho2TiO5, most tetrahedra are magnetically incomplete because some tetrahedral vertices are occupied by nonmagnetic Ti rather than Ho; nevertheless, the dominant incomplete configurations are 2-in/1-out and 1-in/2-out, which are locally compatible with the ice rule if the missing Ho spin is restored. The single-ion <111> Ising anisotropy is therefore retained throughout, while the collective ice ordering is strongly disrupted: Ho2TiO5 is a vacancy-disrupted spin ice in which a local ice-rule tendency persists on a topologically incomplete magnetic network.
