More than 130 line peaks in electron spin resonance spectra were discovered in MgF2 crystals during room-temperature experiments. A sample was cut from the shoulder part of the MgF2 crystal and another was from a MgF2:Co crystal. The same anisotropic electron spin resonance spectra of the 2 samples indicated that the Co2+ dopant introduced defects which introduced the same multinuclear free radicals as in dislocations in the MgF2. These paramagnetic solid multinuclear free radicals exhibited good stability and their electron spin resonance spectra were found to be anisotropic. Electron spin resonance signals were obtained from 3 different types of multinuclear free radicals using a tentative simulation analysis. When the direction of the applied magnetic field was along the [100] or [010] orientation of the crystal, the magnetic field at which the electron spin resonance signals were detected ranged from 0.2294T to 0.4654T and the width of this range was 0.2362T (corresponding to an energy band of 0.233eV). The most narrow peak in the electron spin resonance spectra had a width of about 1.28 x 10-3T. This width, equivalent to the energy difference of 2 neighboring levels, was very small; being only 1.85 x 10-7eV (or 1.46 x 10-3/cm). This indicated that the ground state was highly degenerate and split into nearly quasi-continuous energy levels; like an energy band in an applied magnetic field.

ESR of Dislocation Defects in MgF2 Crystals with More Than 130 Line Peaks. B.H.Hou, Y.G.Zheng, M.Shao, F.Y.Liu, Z.D.Fan: Chinese Physics, 2005, 14, 1453-6