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.

Electron paramagnetic resonance, composite materials, linewidth, spin–lattice relaxation, spin–spin relaxation, concentration effect.

Abragam, A. (1961). Principles of Nuclear Magnetism. Oxford University Press.

Poole, C.P. (1996). Electron Spin Resonance. Wiley.

Weil, J.A., Bolton, J.R. (2007). Electron Paramagnetic Resonance. Wiley.

Камалова Д.И., Умаров А.В., Негматов С.С. Исследование колебательного спектра композита на основе полистирола и сажи //Новые композиционные и нанокомпозиционные материалы: структура, свойства и применение: Матер. Респуб. научно-техн. конф. –Ташкент: ТашГТУ ГУП «Фан ва тараккиёт», 5-6 апрелья, 2018.

Kamalova Dilnavoz, Umarov Abdusalom, Negmatov Soyibjon. EPR – spectroscopic research of structure of soot filled polystyrene //IJARSET. International journal advanced research in science, engineering and technology. India, 2019. Volume 6. Issue 5.

Kamalova Dilnavoz, Umarov Abdusalom, Negmatov Soyibjon, Abed Nodira, Negmatova Komila. Thermal conductivity of soot filled compositions based on polystyrene //IJARSET. International journal advanced research in science, engineering and technology. India., 2018. Volume 5. Issue 9.