Heusler compounds are a remarkable material, a vast collection of more than 1000 members with a large number of functionalities. The prototype Cu2MnAl is a ferromagnetic compound, even though none of its elemental constituents are magnetic. This is typical for this material class; the properties of many of the Heuslers can be forecast simply by counting the number of their valence electrons. Most of the Heusler compounds with 8, 18 or 24 valence electrons are semiconductors. The band gap can be tuned from more than 4 eV to zero by changing systematically the composition and simultaneously the lattice constant. Co2-Heusler compounds with more than 24 valence electrons are half-metallic ferromagnetic. Such compounds display nearly full spin polarized conduction electrons making them very useful for spintronics. Mn2-Heusler compounds show excellent performance for spin torque transfer applications. Another class of Heusler compounds has been predicted to be topological insulators, a new quantum state of matter. The precondition for my ambitious proposal was our systematic investigation of the Heusler family, which has led to detailed insight into the structure- electronic structure to property relation. The short term vision of this proposal is the design, synthesis and investigation of building blocks based on the Heusler structure with combined functionalities; such as superconducting topological insulators. With a virtual lab approach the materials with a desired property will be designed. The large number, the tuneability and controllability of the properties makes this material class the ideal system for the design of artificial multifunctional material on an atomic scale which allows contactless switchable functionalities via external control by fields, current, temperature, or other physical quantities. The long term vision is the synthesis of such an artificial material made by thin film or chemical methods for future electronics and energy technologies.
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Funding SchemeERC-AG - ERC Advanced Grant