Motion ofMn++-Cation Vacancy Pairs in NaCl: Study by Electron Spin Resonance and Dielectric Loss

Thermal motion of the bound positive ion vacancy around a ${\mathrm{Mn}}^{++}$ ion in NaCl has been detected as a broadening of some of the multiplets in the ${\mathrm{Mn}}^{++}$ spin resonance spectrum. In addition, dielectric loss measurements at radio frequencies reveal a Debye loss peak which can be directly correlated with this motion. Analysis of these experiments gives the lifetime of the vacancy in the cation site nearest the ${\mathrm{Mn}}^{++}$ to be $\frac{1}{\tau }=1.2\mathrm{}\times {10}^{14}\exp (-\frac{E}{\mathrm{kT}})$, with $E=0.63\mathrm{}\mp 0.05$ ev. Near 300°C, the lifetime of the vacancy in the next nearest site is approximately one-third less. The ${\mathrm{Mn}}^{++}$-vacancy interchange is not detected in the resonance and therefore does not set in first. The magnitude and form of the loss peak is in good agreement with the recent theory of Lidiard if the effect of both nearest and next nearest pairs is considered.