Electric broadening of the electron paramagnetic resonance lines of Cr3+ in zinc tungstate

Abstract

The parameters describing the linear effect of an electric field on the X-band electron paramagnetic resonance frequency of the impurity Cr3+, charge compensated by Li+, in zinc tungstate have been measured. This allows an explanation of the anomalous behaviour of the resonance linewidth when the magnetic field is rotated in the magnetic zx plane. The linewidth in specimens of high Cr3+ concentration is almost entirely due to the internal electric fields arising from the charged impurities Cr3+ and Li+ acting via the linear electric field effect. The resulting linewidth arises from the equal and opposite shifts in the resonance frequency for the two non-equivalent sites for Cr3+ in the zinc tungstate lattice. The root-mean-square internal field has been measured and agreement found with the value calculated by assuming the Li+ and Cr3+ ions to be randomly distributed throughout the lattice. A specimen of lower Cr3+ concentration has been investigated, and an explanation of the complete behaviour of the linewidth in terms of a simple model is presented.

Linear electric field effect measurements of variant low-spin forms of ferric cytochrome c

“…Essentially the epr line is broad where the LEFE is large. This is a phenomenon which has already been observed in a number of inorganic crystals doped with paramagnetic ions (Mims and Gillen, 1966;Bugai et al, 1967;Jones et al, 1968) where it is interpreted as line broadening due to the presence of internal randomly oriented electric fields in the sample. In the case of ionic crystals the fields originate from point defects in the crystal lattice.…”