Novel Materials Laboratory

Department of Physics

Department of Chemistry

Division of Materials Science and Engineering

Research Projects

Rare-Earth Nitrides


The rare-earth nitrides form a closely related family of magnetic semiconducting or semimetallic materials, exhibiting interesting properties because of the strongly correlated 4f electrons. We use our array of spectroscopic techniques to measure the electronic structure of rare-earth nitride thin films grown in-situ, as well as films capped with suitable protective layers grown by our collaborators in New Zealand: Professors Joe Trodahl and Ben Ruck from Victoria University. The spectroscopies provide unique and complementary information on the energy position, splitting and degree of hybridisation with other states of the occupied and empty 4f- states.  Resonant inelastic x-ray scattering provides additional insights into the excited states of the 4f system and into other many-body effects related to these strongly correlated electrons.  Calculations of the electronic structure are undertaken using the LSDA+U approach (local spin-density approximation complemented with orbital dependent Coulomb and exchange interactions) and implemented in the full-potential linear muffin-tin orbital method by Professor Walter Lambrecht from Case Western Reserve University.  Calculations of the spectroscopic quantities are being developed to extract the maximum information from the experiments. The theoretical analysis of the spectra will identify the need for theoretical developments beyond the mean-field approximation embodied by current LSDA+U, such as integrating atomic multiplet splitting theory with band structure approaches and dynamic mean field theory.  Furthermore, calculations of optical conductivity from interband transitions are carried out and correlated with measurements of the same quantity from the infrared to the near UV to be carried out by the NZ group. The calculations also tie the electronic structure to magnetic properties by calculation of the magnetic exchange parameters.