Many magnetic materials exhibit resonance phenomena in the far infrared frequency range, between 10- 100 cm-1 (or 0.3-3 THz). The experimental studies of these ecitations allows the determination of basic magnetic parameters, like exchange constants, magnetic anisotropy, g-factors, etc. The application of the magnetic field significantly enhances such characterization by analyzing the two-dimensional map of resonance frequencies vs magnetic field. Here I am going to show several examples of the studies:

-         Zero-field splitting in single ion magnets.

-         Magnetic structure of skyrmion material Cu2OSeO3.

-         Antiferromagnetic resonance in multi- sublattices antiferromagnet Ca2Fe2O5.

Also, I will report on the status and recent developments of high-field infrared magneto-spectroscopy instrumentation at the National High Magnetic Field Laboratory.