ELECTRIC-FIELD EFFECTS IN THE EPR OF TETRAHEDRALLY COORDINATED CR5+ IN SRTIO3

This paper reports on electron paramagnetic resonance experiments of t etrahedrally coordinated Cr5+ in SrTiO3, under the influence of applie d static electric fields. At 77 K, the applied electric fields induce an alignment of the off-centre Cr5+ ions along the direction of the el ectric field. The alignment is caused by a linear coupling of the elec tric dipole moment associated with the off-centred Cr5+ ion within the octahedron of surrounding O2- ions and the applied static electric fi eld. From the measurements an electric dipole moment of mu = 2.88 x 10 (-30) C m and an off-centre displacement of about 0.04 angstrom could be determined. Previous results of stress experiments for the Cr5+:SrT iO3 system, at 77 K, have also been considered; for Cr5+ under stress an elastic dipole model is inferred. A differential stress coupling co efficient beta[110BAR] = 4.19 x 10(-24) cm-3 has been determined.