Electron paramagnetic resonance of the [Be]+ centre in MgO:Be

In Be-doped MgO crystals, a new hole centre has been discovered whose physical properties are similar to those of [Li]0-type centres (a hole localized at a cation impurity). The centre can be observed best by electron paramagnetic resonance (EPR) at liquid He temperature; thermal destruction of the centre through the loss of a hole takes place at about 160 K. The symmetry of the centre is almost tetragonal, with a slight rhombic distortion, and the hyperfine structure of its EPR spectrum suggests the following model for the centre: Be2+-O-. However, a detailed investigation of the temperature dependence of the EPR spectrum did not reveal, contrary to our preliminary announcement, any temperature averaging. At higher temperatures the spectrum is complicated by the wealth of spectral lines induced by the ubiquitous Be impurity ions. In particular, this led to our former misinterpretation. The physical properties of the observed centre are discussed and compared with those of analogous centres in MgO