The effect that finite lattice spacing has upon the ESR Bloch equations

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Abstract
The ESR Bloch equations are rederived within a model which allows for finite lattice spacing. It is found this causes the usual Bloch equations to be modified. The internal field as seen by the local moments is changed from Hext+ lambda Me to Hext+ lambda Me+ alpha Me where alpha = lambda 2( Sigma i not=jF1(Rij)- chi e0) and where Hext is the total external field, lambda is the molecular field constant, F1(R) is the usual RKKY range function, chi e0 the static conduction electron susceptibility and Rij is the distance between the sites i and j. The effect this change has upon various limits of physical interest is investigated, compared with the previous results and the experimental data for Mg-Gd is discussed. Finally, the effect of short range correlations in dilute alloys is discussed and a set of generalized Bloch equations are proposed to account for the effects of such correlations in systems which exhibit structured resonances.