Paramagnetic Resonance Line Shapes ofFe++in MgO

The asymmetric $\Delta M=2\mathrm{}$ paramagnetic resonance line shapes of ${\mathrm{Fe}}^{++}$ in MgO are explained using a model of stochastic distributions of cartesian strain components as a strain-broadening mechanism. Strains broaden the $\Delta M=2\mathrm{}$ resonances at lower frequencies by means of a direct zero-field splitting and at higher frequencies by means of a strain-induced change in $g$ value. It is found that this model of broadening gives mathematical expressions for the $\Delta M=2\mathrm{}$ line shapes which agree quantitatively with experimental results.