Quantum-mechanical calculations are today a well-established research approach for the study of new advanced materials. Therefore, the scientist from the Department of Structural and Phase Analysis used it in their scientific work for the prediction of material properties or phase stability without knowledge of any empirical data. Institute of Materials Science and Engineering employs quantum-mechanical calculations for research of multiferroic materials, which are so called “smart” multifunctional materials exhibiting at least two ferroic ordering in a single phase. It makes these materials an ideal candidate for applications like sensors, actuators, or energy harvesting.
One of the multiferroic materials theoretically studied at our Institute are compounds with a structure derived from double perovskites A2BB'O6, which, in addition to ferroelectric and ferromagnetic ordering, can be suitable candidates for spintronic applications. Our calculations allow us to determine the magnetic exchange interaction parameters between atoms, which can be used as inputs to Monte Carlo simulations and predict, for example, the Curie temperature or other magnetic properties. This research is being carried out in collaboration with the Université de Rouen Normandie in France and Kanazawa University in Japan.
Another studied multiferroics are magnetic shape memory alloys based on the Heusler alloy Ni2MnGa. This material exhibits a complex crystal structure with modulation of lattice plains and hierarchically twined microstructure which allows very easy reorientation of twin variants. It results in spontaneous macroscopic deformation of the sample up to 12 % in a moderate magnetic field. Although the crystal structure is the key to understanding such outstanding properties, it is not fully known yet and published results are contradictory. Using quantum-mechanical calculations, we were able to describe transformation paths between different phases and compositional dependence of elastic properties or magnetic anisotropy. The main result is the finding of proper approximation for exchange-correlation energy in quantum-mechanical calculations necessary for obtaining of experimentally observed ground state crystal structure. It is an important step for further simulations with the help of artificial intelligence and machine learning. This research is being carried out in collaboration with the Institute of Physics and Institute of Thermomechanics of Czech Academy of Sciences in Prague and also with LUT University in Lappeenranta, Finland or Institute of Metallurgy and Materials Science, Polish Academy of Sciences in Krakow, Poland.
Contact person:
Martin Zelený, dr.