Manifestation of non-centrality effect in the EPR spectrum of Fe3+ ion in the polycrystalline materials

Abstract

In a number of works [1–6], the study of the electron paramagnetic resonance (EPR) spectrum of polycrystalline non-organic and organic matters revealed presence of EPR spectrum of impurity Fe3+ ion which has essentially different forms at helium and room temperatures. At the helium temperature intensity of the resonance line with g-value close to g1 ≅ 4.3 prevails (Line 1 of the low temperature spectrum). The resonance line with g ≅ 4.3 corresponds to magnetic center with spin S = 5/2 by the spin Hamiltonian parameter D ≫ hv. The resonance line with g-value close to 2.0 (Line 2 of the high temperature spectrum) prevails at the room temperatures. The resonance line with g2 ≅ 2.0 corresponds to magnetic center with spin S = 5/2 by the spin Hamiltonian parameter D ≪ hv. The transition from the low- to high-temperature spectrum is gradual and it is accompanied by a redistribution of the absorption intensity. The observed properties of the temperature dependence of the EPR spectrum are characteristic of systems with a multiminimum potential. The described effect of change of integral intensity of low-temperature and high-temperature EPR spectrum of Fe3+ ion is investigated in substances Na[FeO6(C10H8N)3], C21H14Br4O5S, C25H30ClN3, Al2[Si2O5](OH)4, polyaniline and polyparaphenylene.