INVESTIGATIONS ON ELECTRONICALLY CONDUCTING OXIDE SYSTEMS .18. EPR STUDIES IN THE SOLID-SOLUTION SERIES MGTIO3-TI2O3 AND MG2TIO4-MGTI2O4

The EPR spectra of the solid solution series Mg(1-x)Ti1-x(IV)Ti2x(III)O3 and Mg(Mg(1-x)Ti1-x(IV)Ti2x(III))O4 are reported. The ilmenite/corundum mixed crystals Mg(1-x)Ti1-x(IV)Ti2-x(III)O3 are characterized by the type occurrence of three distinguished types of EPR signals. Spectrum (A) as a broad signal is the only one also found in the spinel type series indicating isolated Ti(III) atoms whose potential energy fluctuates by randomness of cation site occupation. Spectrum (B) has to be interpreted by magnetic dimers resulting from a special kind of pairwise ordering typical for the ilmenite/corundum type structure. Signal (C) is assumed to be caused by defects in the kind of chain-like interaction existing around thc composition Mg0.5Ti0.5(IV)Ti(III)O3.