triplet state the lowest of which is split by spin–orbit coupling to give a ground state Kramers’ doublet with g = 4.33. The next excited states are only a few hundred wavenum bers higher in energy. Distortio ns which lower the symmetry, mix these states. Therefore, the g values become anisotropic and are sensitive to variations in the crystal field [37]. In the present investigations ofCo2+ doped ZnO nanopowde r, the room temperature characteristic EPR spectrum was shown in Fig. 7. The spectrum exhibited unresolved single resonance signal at g = 2.6 which is an indication of Co2+ ions in distorted octahedral symmetr y and this resonance is due to a random distribution of distortions [38–41] in the sample.