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首页> 外文期刊>Physica, B. Condensed Matter >Muon spin relaxation studies of critical fluctuations and diffusive spin dynamics in molecular magnets
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Muon spin relaxation studies of critical fluctuations and diffusive spin dynamics in molecular magnets

机译：分子磁体中的临界涨落和扩散自旋动力学的Muon自旋弛豫研究

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Systematic studies of magnetic critical exponents in local moment molecular magnets can be made by combining three different types of mu SR measurement; zero-field precession, longitudinal relaxation and the frequency shift in transverse field. Systems have been studied with 1D, 2D and 3D structures, having both simple and non-collinear magnetic interactions and the measurements have included investigation of the effect of chirality on the critical spin fluctuations. In the case of the model S = 1/2 Heisenberg antiferromagnetic 1D chain Heisenberg antiferromagnetic quantum critical fluctuations suppress magnetic ordering and TCNQ radical ion salts can provide some excellent examples of this model. In particular, DEOCC-TCNQF(4) behaves as a nearly ideal case with no ordering seen down to 20 mK even though the intrachain exchange interaction is 110K. In contrast the DMTzNC-TCNQ compound orders at 1.5 K, but still shows evidence for significant residual quantum fluctuations in its ordered state in the form of a large suppression of the magnitude of the ordered part of the magnetic moment. From analysis of the characteristic field dependent muon relaxation behaviour as a function of temperature above the transition, the nature of the spin fluctuations is found to change as the transition is approached, suggesting a crossover either to 2D diffusion or to I D ballistic motion.
机译：通过结合三种不同类型的mu SR测量，可以对局部矩分子磁体中的磁性临界指数进行系统研究。零场进动，纵向弛豫和横向场的频移。已经对具有1D，2D和3D结构的系统进行了研究，这些结构具有简单的和非共线的磁性相互作用，并且测量结果包括研究手性对临界自旋涨落的影响。在模型S = 1/2的情况下，Heisenberg反铁磁1D链Heisenberg反铁磁量子临界波动可抑制磁性排序，而TCNQ自由基离子盐可提供该模型的一些出色实例。特别是，即使链内交换相互作用为110K，DEOCC-TCNQF（4）的表现也很理想，在低至20 mK的情况下都没有排序。相比之下，DMTzNC-TCNQ化合物的序数为1.5 K，但仍以大量抑制磁矩有序部分的形式显示了其有序状态中存在明显的残余量子涨落的证据。通过分析与跃迁上方温度有关的，取决于特性场的介子弛豫行为，可以发现随着接近跃迁，自旋涨落的性质会发生变化，这表明与2D扩散或1D弹道运动有交叉。

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