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

• Applicants: Professor Dr. Stefan Süllow; Dr. Anja Wolter-Giraud, Ph.D.
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2010 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 161578921

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.

• DFG Programme: Research Grants
• International Connection: Australia
• Cooperation Partner: Dr. Kirrily Rule