Uni Koeln
Transition-metal oxides and chalcogenides exhibit a plenty of highly diverse functional material properties prospective for application. This variability results from the balance of competing interactions between correlated microscopic degrees of freedom (spin, charge, orbital, structure). This sensitive balance often can be influenced by only small external fields and reaches from highly frustrated ground states to multiferroic order. The low-lying excitations and collective modes in such complex phases demand for a spectroscopic window bridging the DC transport and thermodynamic material properties and the usual phononic and electronic energy scales. The phenomenology reaches from glassy relaxational features to the search for collective magneto-electric excitations in multiferroics, so called electromagnons. The talk will introduce the experimental approaches for broadband dielectric spectroscopy which shall be utilized to cover the frequency range from the mHz to the THz and will illustrate it considering selected investigations on (rare-earth) manganites and (thio-)spinel systems.