Electric field effects in EPR of the SrTiO3 :Cr5+ Jahn-Teller system

It is shown that a static electric field affects the intensity ratio of the EPR lines of Cr⁵⁺ (d₁) in SrTiO₃ at 77K. The experimental results can be accounted for quantitatively by considering for the ${}^2\text{T}{}_{\mathrm{2g}}$ electronic ground state of Cr⁵⁺ a strong Jahn-Teller interaction with localized ρ_g mode. The degeneracy of the resulting vibronic ground state is lifted appreciably by a macroscopic strain which, as a result of the large electrostrictive coupling in SrTiO₃, is induced at moderate electric field strengths.