Combining experiment and theory to characterize new intermetallic compounds
Our experimental efforts currently involve high-temperature synthesis, e.g., arc-melting or solid state reactions. We also carry out reactions in metal fluxes. We focus particularly on new complex transition metal borides. These materials usually show not only exciting crystal structures but also very interesting magnetic and superconducting properties.
Our theoretical endeavors concern almost first principles electronic structure calculations. We use mainly LMTO (linear muffin- tin orbital), LAPW (linear augmented plane wave) and modified pseudo-potential (VASP) calculations to investigate patterns of atomic arrangements and magnetic order. In this area we strongly collaborate with the research group of Professor G. J. Miller (Iowa State University, USA).
Relationships between valence electron count and magnetic order
We study complex borides that show magnetically active 3d metals (Cr, Mn, Fe, Co, Ni) in low-dimensional environments, such as wires and ladders. We have shown relationships between valence electron count and magnetic order (ferromagnetism vs. antiferromagnetism), and are using both COHP ("overlap population") strategies as well as evaluation of effective two-center exchange parameters to rationalize and predict magnetic order in these complex solids.
Structural characterization using X-ray powder and single crystal diffraction
X-ray diffraction is our primary technique to examine the physico-chemical make-up of unknown solids. We therefore use this technique not only to identify new phases and new crystal structures during our research, it is also a service we offer to other collaboration partners. For example we elucidate the structural arrangement of some transition metal complexes showing nanochannels containing water molecules in a highly disordered arrangement (collaboration with Professors J. Nenwa and M. M. Belombe, University of Yaoundé I, Cameroon). Another example is the investigation of some complex oxoselenoantimonates semiconductors (called cetineites) also showing nanochannels which can be filled with noble gases (collaboration with Professor U. Simon, RWTH Aachen University, Germany).