How and Why the characterization of magnetic materials can give directions in the methodological development in high field - high frequency EPR.

The experimental problems linked to the use of the ultra-wide band high field-high frequency Electron Paramagnetic Resonance (HF2-EPR) spectrometers are illustrated with some key examples. The single pass technique is critically analyzed and compared with other techniques. Propagation and magnetic field dependent phenomena are illustrated with the aid of three key examples and discussed. The possible actions to be taken in order to minimize and possibly eliminate these extrinsic effects affecting the spectra obtained with the single pass technique are proposed. Future instrumental developments are discussed in the light of the experience acquired in this study.