CONCENTRATION DEPENDENCE OF EPR LINEWIDTH, SPIN–LATTICE AND SPIN–SPIN RELAXATION TIMES IN COMPOSITE MATERIALS

This study investigates the concentration dependence of electron paramagnetic resonance (EPR) linewidth (ΔH), spin–lattice relaxation time (T1), and spin–spin relaxation time (T2) in composite materials containing paramagnetic centers. Theoretical analysis and experimental considerations demonstrate that increasing paramagnetic center concentration enhances dipole–dipole and exchange interactions, resulting in linewidth broadening and reduction of relaxation times. Exchange narrowing effects at higher concentrations are also analyzed. The results are relevant for the characterization of functional composite materials and magnetic systems.