Density functional theory calculations performed for the new multiferroic FeTe2O5Br reveal surprisingly strong super-superexchange pathways through Fe-O-Te-O-Fe bridges, implying that the magnetic lattice must be treated as a system of alternating Fe chains coupled by frustrated interactions. We find firm support for this model in the magnetization and the antiferromagnetic resonance measurements as well as in the matching of the incommensurate magnetic vector. Its peculiar temperature dependence is explained by interchain exchange-striction being responsible for the emergent net electric polarization.
B.04 Guest lecture
COBISS.SI-ID: 24455975Overview of magnetic resonance is given at the level of PhD students. Special emphasis is on the spin interactions that are relevant in metallic and magnetic systems and main expressions for the spin-lattice relaxation time and resonance shifts are derived. These results are applied to numerous experimental results.
B.05 Guest lecturer at an institute/university
COBISS.SI-ID: 24819495In this contribution report we address the issues of Ga site-occupancy, rattler site-selectivity and bonding to the lattice as well as their effects on the electronic structure by employing local probe NMR technique. We find firm evidences for the rattler to interact more strongly with a particular (24k) site, possibly even forming weak covalent bonds. Strikingly, local charge density for this site is also affected suggesting that the anharmonic rattling vibrations are involved in the electron-phonon coupling. These results have implications not only for the thermoelectric response of clathrates but also for the unconventional superconductivity observed in certain clathrate compounds.
B.04 Guest lecture
COBISS.SI-ID: 25429799