Concentration-Dependent Electron Spin Resonance

A number of workers have studied the decrease of the intensity of a nuclear magnetic resonance (NMR) line as one adds impurities to the specimen. Usually the intensity of the line is $\propto {\mathrm{}(1-c)\mathrm{}}^n$, where $c=\mathrm{the}\mathrm{concentration}\mathrm{of}\mathrm{the}\mathrm{impurities}$ and $n$ is the so-called wipe-out number, i.e., if the impurity is within a sphere containing $n$ neighboring positions its effect is large enough so as to cause a nuclear quadrupole splitting of the host nuclei so that they no longer contribute to the NMR line. Experimentally one can determine $n$. The extension of this type of experiment into the domain of electron spin resonance (ESR), in a very simple way, is described. Also, the wipe-out number for ${\mathrm{Mn}}^{2+}$ in two systems, $({\mathrm{Zn}}_{1-c}+{\mathrm{Cd}}_c)\mathrm{S}$ and $\mathrm{Zn}({\mathrm{S}}_{1-c}+{\mathrm{Se}}_c)$, is measured. One finds $n=157\mathrm{} \mathrm{and} 270$, respectively.