Novel Caloric Materials by Mastering Hysteresis: Combinatorial Development of Magnetocaloric Materials

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This project is part of the of the package proposal “Novel Caloric Materials by Mastering Hysteresis”, which aims for the optimization and development of new magnetocaloric materials. Therefore, the known magnetocaloric systems La(Fe,Si)13, Fe2P und Co-Mn-Ge will be fabricated as complete thin film materials libraries in this project. Automated high-throughput methods will characterize these materials libraries regarding chemical composition, crystal structure, electrical resistivity and magnetic properties. The aim is to identify regions, which show a reversible magnetic/structural transformation and are ferromagnetic. In a next step a variation of fabrication and processing (annealing temperature and atmosphere, dwell time and cooling rate) parameters will be used to change the microstructure, in order to adjust solubility, hysteresis width, magnetic properties and transformation temperatures. By the addition of further elements, that partially alloy interstitial into the lattice, the materials properties will be adjusted by changing the inter-atomic distance and chemical order. These elements will be chosen partially on results from density functional theory calculations performed in close collaboration within the consortium. The combinatorial approach allows for a systematic investigation of complex materials systems (ternary, quaternary and quinternary alloys) in regard to the structure-property-relationship. These systematic investigations of complex systems provide the development of heuristic trends and thus a deeper understanding. Samples with optimized properties will be given to consortium partners for extended experimental investigations. A further objective is the direct measurement of adiabatic temperature change in thin film samples by using micro-machined substrates. Additional investigations on corrosion resistance and fatigue will provide the development of complex materials with optimized properties regarding future magnetic refrigeration application.