Unconventional spin freezing and fluctuations in the frustrated antiferromagnet NiGa 2 S 4
Unconventional spin freezing and fluctuations in the frustrated antiferromagnet NiGa 2 S 4
复制标题
DOI：
10.1103/physrevb.78.220403
复制
发表时间：
2008-11
影响因子：
3.7
通讯作者：
D. MacLaughlin;Y. Nambu;S. Nakatsuji;R. Heffner;L. Shu;O. Bernal;K. Ishida
中科院分区：
文献类型：
--
作者：
D. MacLaughlin;Y. Nambu;S. Nakatsuji;R. Heffner;L. Shu;O. Bernal;K. Ishida
介子自旋旋转实验揭示了二维三角形晶格反铁磁体NiGa2S4中的非常规自旋冻结和动力学。长寿命无序Ni-自旋冻结(关联时间>；10-6 S，2 K时)在T_f=8.5±-0.5K以下发生，具有类平均场的温度依赖关系。观测到的T_f以上介子自旋弛豫的指数温度依赖关系是2D临界自旋涨落的有力证据。在低温下，缓慢的Ni自旋涨落与准静态磁性共存，但在10mT的磁场中，Ni自旋涨落很快被抑制，这与场无关的比热形成鲜明对比。MuSR和体磁化率数据表明，NiGa2S4在T_f处存在明显的2D相变，低于此相变温度时，NiGa2S4既不是传统的磁体，也不是单态自旋液体。
Muon spin rotation (muSR) experiments reveal unconventional spin freezing and dynamics in the two-dimensional (2D) triangular lattice antiferromagnet NiGa2S4. Long-lived disordered Ni-spin freezing (correlation time > 10-6 s at 2 K) sets in below T_f = 8.5 +- 0.5 K with a mean-field-like temperature dependence. The observed exponential temperature dependence of the muon spin relaxation above T_f is strong evidence for 2D critical spin fluctuations. Slow Ni spin fluctuations coexist with quasistatic magnetism at low temperatures but are rapidly suppressed for fields > 10 mT, in marked contrast with the field-independent specific heat. The muSR and bulk susceptibility data indicate a well-defined 2D phase transition at T_f, below which NiGa2S4 is neither a conventional magnet nor a singlet spin liquid.