Tetrahedrally coordinated Cr⁵⁺ in SrTiO₃

This paper reports on the electron paramagnetic resonance angular variation of the S = 1 2Cr5+ center with orthorhombic symmetry, obtained after quenching Al and Cr-doped SrTiO3 from 1400 °C. At 4.2 K, the main axes of the g-tensor in monodomain {001} samples are found to be along [001] and rotated by ± α = 2φ{symbol} = 4° from 〈110〉 axes, where φ{symbol} is the intrinsic structural phase transition (SPT) order paramater. From this and the size of the g-values as well as stereometrical considerations, an assignment of the small Cr5+ ion to a tetrahedral site in the perovskite structure is made. Above the tetragonal-to-cubic SPT at Tc = 105 K, a dynamic reorientation among the six equivalent sites is observed, and below Tc, a deviation from α(T) = 2φ{symbol}(T) between 70 K < T < Tc. © 1993.