Budapest University of Technology and Economics

Budapest University of Technology and EconomicsBudapest University of Technology and Economics (BME) is one of the five Elite Research Universities in Hungary with a focus on engineering and natural sciences.

The Department of Theoretical Physics exhibits a broad research activity in the area of theoretical and computational solid state physics, statistical physics, quantum chemistry and quantum information. Most of this research is funded by the Hungarian National Research Foundation and the European Commission through the FP7 scheme.

The group of Prof. L. Szunyogh has a great experience with ab initio calculations of electronic and magnetic properties of solid magnets, thin films and finite nanoparticles, including exchange interactions and magnetic anisotropy, magneto-transport (GMR, TMR, AMR), and ab initio spin-dynamics.

The group has also worked on different aspects of multiscale modelling, an effort to link ab-initio calculations, spin model simulations, and large-scale micromagnetic methods. Research highlights include exchange bias in nano-structured compounds of antiferromagnetic and ferromagnetic materials, multiscale modelling, ultrafast spin dynamics and spintronics. Project relevant numerical methods currently used in the applicant’s group include Monte Carlo simulations, numerical solutions of stochastic differential equations, and micromagnetic modelling. Modern and highly  optimised computational approaches are provided to scale down the numerical effort. These calculations are currently performed on the high-performance computer cluster of the group (currently about 200 compute nodes).

Members of the BME group worked out a relativistic method to calculate tensorial exchange interactions and paid special attention to evaluate interactions in magnetic nanostructures. These ab-initio based interactions can in turn be used as input parameters in atomistic simulations based on the Monte-Carlo method or the solution of Landau-Lifshitz-Gilbert equation. This theoretical approach has been used so far to study the complex magnetism of bulk FM and AF compounds, AF-FM interfaces and thin magnetic films.

BME is responsible for the atomic modelling of the Heusler alloys, where alloy structures will be modelled using ab initio calculations they have developed. The Heusler alloy unit cells are modelled and their antiferromagnetic anisotropies are calculated to be fed back to alloy selection. The atomic modelling also utilises experimental parameters measured at the later stage of the project to establish a new consistent modelling for alloys.

BME will perform a systematic ab initio study of the structural and magnetic properties of ferromagnetic and antiferromagnetic Heusler alloys, as well as of systems formed by them, such as FM-AF interfaces and multilayers. Spin model parameters, exchange interactions and anisotropies, obtained from these calculations will serve as input to multi-scale modelling by UKON, thus a very intense exchange of the results and expertise is planned between BME and UKON. The outcome of these calculations will then be compared to experiments performed in UNIBI, TOH and UoY, from which we expect to increase the functionality of the sensor devices based on Heusler alloys.