Determination of new sites for two Fe³⁺EPR centres in KTiOPO₄

Abstract

EPR spenra of Fe3+ ions in single crystals of KliOPOr (KTP), synthesized by the Eux method, have been investigated at mom temperature by employing a Bruker Q-band spectrometer. From the angular dependence of the EPR spectm two Fe3+ centres denoted as C1 and C2 have been identified, in agreement with the previous analysis by other investigators. In this study, for the first time we have fully identified two groups of four magnetically inequivalent Fe3+ sites each belonging to the centres C1 and C2. Two sets of triclinic spin-Hamiltonian parameters, which simultaneously fiited EPR data for the four sites belonging to the centres C1 and Q, were determined. The direction cosines of the principal axes of the g-tensor as well as the second-order zero-field splitting (ZFS) tensor are found to be given by the relations: Imn, imn, lrirn, and i%n for each four F$+ sites of C1 as well as C2, respectively, consistent with the crystallographic point group mm2 of KTP.

A Comparative High-Resolution Electron Microscope Study of Ag Clusters Produced by a Sputter-Gas Aggregation and Ion Cluster Beam Technique

“…The EPR measurements were carried out at room temperature by employing a Bruker Q-band spectrometer [12,14]. It is critical to establish an accurate crystal orientation with respect to the applied magnetic field in order to properly classify several centres having similar EPR parameters and all four fine structures belonging to each centre.…”

“…Two sets of fine-structure lines became degenerate forming one set when the magnetic field B was applied in each of the crystallographic planes ab, bc, and ca. All four sets due to each of Cr 3+ and Fe 3+ at the four magnetically inequivalent sites merged completely into one when B was aligned along each of the crystal axes a, b, and c. This made it possible to establish crystal alignments within ±0.05 • in the three planes by adjusting the crystal orientation inside the cylindrical cavity in such a way as to achieve degeneracy of the EPR lines [12,14]. The EPR spectra were recorded by varying the orientations of B in the three planes from 0 • to 180 • in steps of 3 • for the Fe 3+ spectra and 4 • for the Cr 3+ spectra.…”

“…On the basis of previous work [16][17][18][19], we were able to identify four Cr 3+ [12,13] and four Fe 3+ [14,15] centres, and all four complete sets of fine structures due to the ions at the magnetically inequivalent sites were systematized in terms of the crystal symmetry of KTP. In this study, an overall comparison between the principal-axis orientations of the g-tensors and the second-order zero-field splitting (ZFS) tensors for Cr 3+ and Fe 3+ centres is made.…”

“…The structure exhibits two crystallographically different Ti sites: Ti(1) and Ti (2), replaced by Cr 3+ and Fe 3+ . Each Ti has four chemically equivalent but magnetically inequivalent sites [12][13][14][15] due to the symmetry elements, characterized by two glide planes n and a and one screw axis 2 1 [10,11].…”

Role of silicon impurities in the trapping of holes in KTiOPO4 crystals

“…[16][17][18][19][20] After exposure to x rays or a 355 nm laser beam at room temperature, most of these Fe 3ϩ and Cr 3ϩ signals decrease and other EPR signals appear. Of the new EPR spectra induced by the x rays or the laser beam, we find that some can be monitored at room temperature while others can only be seen at lower temperatures.…”