Magnetic field induced phases in one-dimensional (1D) antiferromagnetic quantum magnets

低维量子磁体表现出许多新的现象，特别是如外来（场诱导）相。特别是对于磁耦合路径的几何挫折的情况下，一些不同的和新的相位已被观察到，而到目前为止，还没有全面的理论理解。因此，关于这个主题，从实验方面有必要对这些阶段进行详细的描述，以便为理论建模定义基准。在这个后续项目中，我们计划研究受挫折的低维量子磁体中的场诱导阶段，因为这些阶段以独特的方式代表了（几乎完全）可计算的模型系统。本项目包括（i）Heisenberg链受抑linarite的场诱导相，以及（II）Kagome系统haydeeite的（压力依赖的）基态性质的研究，在前一项目中，我们首次用微观和宏观技术对LinaritPbCuSO_4（OH）_2系统进行了广泛的表征。作为我们研究的结果，我们可以将材料建模为受抑自旋链，具有铁磁最近邻和反铁磁次近邻耦合。此外，对于第一个阶段，我们已经确定了一系列新的阶段，这又带来了一系列新的科学课题。我们现在要详细讨论这些问题。此外，在第二个子项目中，我们计划详细研究受挫折的Kagome晶格haydeeite Cu_3Mg（OH）_6Cl_2的性质。从最近的出版物中发现，有显着的理论预测和实验观察之间的差异。此外，实验观察本身既不是完全成立的，也没有矛盾。根据我们在确定这种阻挫磁体中的复杂状态的经验，我们希望对haydeeite的性质进行相应的研究。为了获得基本现象的全面和连贯的想法，在这两种情况下，我们计划将联合收割机热力学研究与微观NMR研究和（内）弹性中子散射结合起来，这是外部参数如压力或磁场的函数。

Low-dimensional quantum magnets exhibit a multitude of novel phenomena, notably such as exotic (field-induced) phases. Especially for the case of geometrical frustration of the magnetic coupling paths a number of different and new phases have been observed, while so far there is no comprehensive theoretical understanding. Therefore, regarding this topic, from the experimental side there is need for a detailed description of such phases, in order to define benchmarks for theoretical modellings.Within this follow-up projects, we plan to investigate such field-induced phases in frustrated low-dimensional quantum magnets, as these represent in a unique manner model systems that are (almost exactly) computable. The project covers studies on (i) the field-induced phases in the frustrated Heisenberg chain linarite, as well as on (II) the (pressure dependent) ground state properties of the Kagome system haydeeite.Within the preceeding project, for the first time we have extensively characterized the system Linarit PbCuSO_4(OH)_2 using micro- as macroscopic techniques. As result of our investigations we could model the material as frustrated spin chain, with a ferromagnetic nearest-neighbor and an antiferromagnetic next-nearest-neighbor coupling. Further, for the first we have identified a series of novel phases, which again brought a series of new scientific topics. These topics we wish to address now in detail. Furthermore, in a second subproject we plan to study in detail the properties of the frustrated Kagome lattice haydeeite Cu_3Mg(OH)_6Cl_2. From recent publications it was found that there are significant discrepancies between theoretical prediction and experimental observation. Moreover, the experimental observations itself are neither fully established nor free of contradictions. With our experience in determining complex states in such frustrated magnets we wish to carry a corresponding study of the properties of haydeeite.To obtain a comprehensive and coherent idea of the basic phenomena, in both cases we plan to combine thermodynamic studies with microscopic NMR investigations and (in)elastic neutron scattering, this as function of external parametters such as pressure or magnetic field.