Neutron Diffraction on Magnetically Frustrated Low-Dimensional Magnets

Abstract:

Low-dimensional magnets are fundamentally different from 3D magnetic materials. Lower-dimensional systems stay disordered in models with continuous symmetry at T ≠ 0 based on the theorem of Mermin and Wagner. Low-dimensional magnets can possess complex phase diagrams and produce exotic magnetic ground states such as spin glasses, spin ices, and spin liquids, due to the combined effects of anisotropy and frustration. Frustrated systems have Hamiltonians with competing interactions that make contributions to the energy that cannot simultaneously be minimized. Competition among magnetic exchange interactions may lead to a strong frustration, resulting in a macroscopic degeneracy of the ground state. The effects of frustration are particularly strongly pronounced in low-dimensional magnets, as both frustration and low dimensionality act to suppress long-range order and enhance quantum fluctuations. Examples of such magnets are spin ladders, spin chains, and two-dimensional honeycomb and triangular magnets. I will discuss three different frustrated systems: Cu ludwigites, antlerite, and KCeS₂ delafossite. These compounds are different representatives of quantum low-dimensional systems with different natures of frustration. We will consider the unusual 1D and 2D magnetic systems’ behaviour by their examples.

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