Inelastic neutron scattering is used to investigate the temperature dependence of spin correlations in the 3-dimensional XY antiferromagnet $\mathrm{Ni}{\left({\mathrm{Cl}}_{1-x}{\mathrm{Br}}_x\right)}_2·4\mathrm{SC}{\left({\mathrm{NH}}_2\right)}_2, x=0.14\left(1\right)$, tuned close to the chemical-composition-induced soft-mode transition. The local dynamic structure factor shows $\hslash \omega /T$ scaling behavior characteristic of a quantum-critical point. The deviation of the measured critical exponent from spin wave theoretical expectations is attributed to disorder. Another effect of disorder is local excitations above the magnon band. Their energy, structure factor, and temperature dependence are well explained by simple strong-bond dimers associated with Br-impurity sites.

中文翻译：

---

有限温度动力学和无序在近临界Ni（Cl1-xBrx）2·4SC（NH2）2中的作用

非弹性中子散射用于研究3维XY反铁磁体中自旋相关性的温度依赖性 $你{（{氯}_{\mathrm{1个}-X}{溴}_X）}_2·4\mathrm{SC}{（{\mathrm{NH}}_2）}_2， X=0.14（\mathrm{1个}）$调整为接近化学成分诱导的软模式转变。局部动力结构因素显示$\hslash \omega /Ť$量子临界点的缩放行为特征。测得的临界指数与自旋波理论预期值的偏差归因于无序。无序的另一个影响是在磁振子带之上的局部激发。它们的能量，结构因子和温度依赖性可以通过与Br杂质位点相关的简单强键二聚体很好地解释。