Electron spin resonance Lorentzian shape

Kittel and Abrahams 12S) have predicted an approximately Lorentzian magnetic resonance line shape for a system of spins which are randomly distributed over a small fraction of a large number of possible sites. This effect has been observed in electron spin resonance (124)- Kittel and Abrahams estimate that appreciable deviations from Gaussian shape will occur when the fraction of sites occupied, f, is less than 0.1, in the case of spins of / = H iu a simple cubic lattice with the magnetic field directed... 

Conclusive additional evidence for the metallic nature of PAni and its blends with PMMA is provided by electron spin resonance (ESR) studies with the observation of a Dysonian line shape [104]. In both cases, the asymmetry ratio (A/B) decreases with decreasing temperature. The observed changes in the line shape from Dysonian to Lorentzian are thus seen to be a manifestation of the variation with temperature of the electrical conductivity (Figure 1.46). The g value is calculated as 2.00191 + 0.00005. The g value, which is close to the fi-ee spin value, confirms that the spins are indeed polarons. 

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