Electron paramagnetic resonance (a review)

For the purposes of this review, the termelectron paramagnetic resonance is taken to refer to the resonant absorption of electromagnetic radiation by electronic systems which possesspermanent magnetic moments (due, in general, to the orbital as well as to the spin angular momentums of electrons) and which are therefore paramagnetic. The termparamagnetic resonance, which is frequently encountered, refers strictly to the magnetic resonance of permanent magnetic dipoles of any type, including nuclear magnetic resonance. On the other hand, the termelectron resonance includes cyclotron resonance (diamagnetic resonance).In a short article of this nature, it is clearly impossible to discuss, in detail, all aspects of such a wide field. Rather, the intention is to discuss the basic principles of the electron paramagnetic resonance technique together with some results in certain fields which illustrate its range, applications, and potentialities.