ELECTRON PARAMAGNETIC RESONANCE OF Co-DOPED PbWO4.

The electron paramagnetic resonance of Co-doped PbWO4 has been observed on a superheterodyne X-band microwave spectrometer at temperatures between 4 degrees K and 15 degrees K. Four groups of EPR spectra were found. These spectra could be mapped into each other by suitable transformations and, hence, were basically the same. The three Eulerian angles characterizing the principal coordinate system of one such group with respect to the crystal axis c a a system are 43.8 degrees, 28.0 degrees and -65.3 degrees. The orientations of the remaining three groups are obtained by successive 90 rotations about the c-axis. In its principal axis system, each spectrum was characterized by an effective spin S equal to 12 and a nuclear spin I equal to 72. From various evidence we conclude that the Co enters the lattice in a 2 state and probably substitutes at a W site. Author