Concentration dependence of the Cr3+ ESR linewidth in barium titanate

The concentration dependence of the electron spin resonance (ESR) linewidth of Cr3+ ions in chromium-doped barium titanate (BaTiO3) was investigated at room temperature for chromium concentrations between 0.10 and 2.00 mol%. According to previous studies, chromium substitutes Ti4+ sites in the lattice and its preferred valence state is Cr4+, which is ESR silent in the X-band. In the present work, the Cr3+ state was enhanced by codoping with Nb, as it has been done previously in a similar compound, SrTiO3. The results show that the concentration dependence of the ESR peak-to-peak linewidth and the relative intensity of the Cr3+ spectrum can be approximated by the theoretical equations ΔHpp = 3.30 + C1(1 − f)80 mT and I = C2f(1 − f)80, where f is the chromium concentration and C1 and C2 are constants. This suggests that the range of the exchange interaction between Cr3+ ions in barium titanate is about 0.96 nm.