The lecture aims at bridging the gap between introductory level courses and modern research fields in solid-state physics. In this lecture, a particular emphasis is placed on the dielectric and magnetic properties of solids. The lecture includes an introduction into the theoretical description of these properties, state-of-the-art experimental methodologies for their characterization as well as some glimpses into modern research areas in this field. The accompanying seminar/exercise consists of classical problem sheets as well as a series of student presentations on selected experimental techniques and highlighted topics.

Contents of the lecture includes:
1. Dielectric properties of solids
• Lorentz model, local electric field, electric polarization, Kramers-Kronig relation, dielectric function, macroscopic electrodynamics
• Examples of optical resonances (plasmons, excitons, band-to-band transitions, phonons, defect transitions)
• Optical spectroscopy (photoluminescence, reflectivity, near-field probes, Raman and THz spectroscopy) and electron beam-based spectroscopy of solids (electron energy loss spectroscopy)
• Electromagnetic waves at interfaces and in thin-films, optically anisotropic media
• Polariton physics: Plasmon-polaritons, exciton-polaritons, phonon-polaritons
• Screening, electron-electron and electron-phonon interactions (Lindhard theory, polarons, Fermi liquid)
• Ferroelectricity (incl. Landau theory of phase transitions)
• Nonlinear dielectric response (SHG spectroscopy, multi-photon-spectroscopy, strong-field effects in solids)
2. Magnetic properties of solids
• Dia- and paramagnetism
• Cooperative phenomena in magnetism
• Spin waves
• Magnetic domains and magnetization patterns
• Experimental methods for imaging magnetic textures (spin-polarized scanning tunneling microscopy, magnetic force microscopy, Lorentz microscopy)
• Magnetization dynamics (Landau-Lifschitz-Gilbert equation) and ultrafast magnetism
• Spintronics