Electron paramagnetic resonance of Ce3+in strontium-barium niobate

The EPR of Ce 3+ in congruent Sr x Ba 1- x Nb 2 O 6 ( x = 0.61) is characterized by the orthorhombic g -tensor {0.89,3.55,0.54} with principal axes lying in the c -plane, tilted with respect to the a - and b -axes by 21.1°, and along the c -axis. Ce 3+ occupies a single crystallographic site in the crystal, leading to a unique EPR spectrum. The point symmetry of the Ce 3+ position, C 1 , is lower than that of the replaced alkaline-earth ions, C 4 or C s . This is attributed to an off-centre movement of Ce 3+ . The Ce 3+ signal decreases under illumination. No further EPR signal is detected to arise from the photoionization of Ce 3+ .