Spin-lattice relaxations of paramagnetic Fe3+ in ZnO

The spin-lattice relaxation rate of paramagnetic Fe3+ in single-crystalline ZnO has been determined following low-fluence (?<1012 cm-2) 60 keV implantation of 57Mn+ (T1/2=1.5 min) and emission Mössbauer spectroscopy on the 57Fe daughter nucleus in the temperature range from 300 to 664 K. The spin-lattice relaxation of Fe3+ is found to follow a T9 temperature dependence, in contrast to the T2 dependence expected for a two-phonon Raman process determined in both single-crystal MgO and ?-Al2O3 using the same analysis method of the Mössbauer spectra measured without an applied external magnetic field. This is an unexpected result since ZnO has a lower Debye temperature than both MgO and ?-Al2O3.