Electron paramagnetic resonance study of a new centre and eight new sites of ions in

Abstract

Careful reanalysis of EPR spectra of ions in (KTP) has been carried out in order to resolve the weaker lines not considered in our previous study. Eight additional sets of fine-structure (FS) lines, (Y = 3, 4 and j = a, b, c, d), have now been identified and their respective spin-Hamiltonian parameters have been determined. These sets are classified into two groups denoted as centres C3 and C4, each of which yields identical principal values of the tensor and second-order zero-field splitting tensor but different orientations of the principal axes. For four sets of FSs belonging to each centre, the direction cosines of the principal axes are found to be , and , consistently with the crystal symmetry of KTP. The FS C4a agrees well with that denoted as the centre ST4 by other investigators, whereas the others are newly identified. The eight magnetically inequivalent sites are assigned to two titanium sites: Ti(1) and Ti(2). Two different centres, C1 and C3 as well as C2 and C4, arising from ions at the respective Ti(1) and Ti(2) sites, are explained by differing charge compensation. It is also suggested that a vacancy of the first-neighbour oxygen OT(1), denoted as , plays the role of a divalent positive charge compensator simultaneously for two ions at the adjacent Ti(1) and Ti(2) sites.