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Support Address: support@nsc.liu.se |
Atomistic spin dynamics in complex magnets
AbstractThe main research directions within the frame of the proposed project concern a thorough investigation of materials with complex magnetic configurations, with emphasis on: (i) surface and relativistic effects, such as surface magnons in chiral magnets and (ii) magnonic devices. [Magnonics is a topic in modern magnetism correlated with spin-wave generation and manipulation in nano-structures. The magnonic materials are formed by periodic repetitions of thin layers or by arrays of nano-structures, such as quantum dots etc.] In connection to these directions, also studies that lead to a deeper understanding of magnetic interactions in complex systems (inter-metallic compounds, complex oxides - where orbital hybridisations are strong) will be pursued. The first studies in the proposed directions regard the investigation and correct description of the magnetic interactions in complex systems (helimagnets and complex oxides), together with a detailed study of their magnetisation dynamics at the atomic-scale. The purpose of these studies is to elucidate the origin of complex magnetic interactions and to describe their static and dynamic behaviour. We shall perform these investigations from a theoretical point of view, aiming to corroborate our results with state-of-the-art experimental data and to motivate with our predictions further experimental studies. We shall make use of an atomistic description of the magnetisation dynamics in addition to fully-relativistic 'ab initio' methods. By correlating these two approaches (which are being constantly improved), we create powerful tools which give insightful information about the physics governing nano-scale magnetization dynamics. This information could prove relevant for finding efficient ways of building nano- scale devices for green information and communication technologies. The theoretical investigations will be performed in two steps. First, by means of fully-relativistis, spin-polarized 'ab initio' methods, the electronic structure and the magnetic properties of the systems under consideration will be described. In the second step, all the information obtained from the first principle calculations is going to be used as starting point for the atomistic spin dynamics simulations (within UppASD). The allocated computational time will be used for simulations describing and investigating the spin-waves excitation spectra at surfaces and in multilayers. The magnon spectra in chiral magnets differ drastically from the ones corresponding to ferromagnetic or antiferromagetic order. We aim at having an accurate description of the magnon spectra in complex magnetic structures and to be able to manipulate the spin-waves. In magnonic systems, the repetitions of different magnetic materials lead to opening of gaps in the magnon spectra. By intimately knowing the characteristics of the spectra, we can tune and control the propagation or blockage of spin-waves with certain frequencies. All the codes and methods that we will use for this project (KKR, FLAPW, UppASD etc) are versatile and their performances have been tested on a wide range of systems and properties. They are well established methods in the electronic structure and spin-dynamics community. KKR-based codes and the UppASD package are already running and are being used with success on Triolith. |
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