Electronic paramagnetic resonance study of Cu2+ ions in copper ion-exchanged layers of lithium niobate crystals

Copper-doped LiNbO3 layers prepared by an Cu-Li ion-exchange process are ch aracterized by electronic paramagnetic resonance. It is found that the majo rity of Cu2+ ions are coupled by strong exchange interactions which is char acteristic of short distances between paramagnetic ions. Such ions are accu mulated in a thin layer near the crystal surface and can enter in new cryst alline phases formed as a result of the Cu-Li ion exchange. A small amount of Cu2+ ions is incorporated into weakly distorted LiNbO3 crystal lattice i nside the diffusion layer.