POINT DEFECTS OF LOW SYMMETRY IN KZnF₃ SINGLE CRYSTALS

Abstract

Resume.-On presente des resultats experimentaux sur des monocristaux de KZnFs dopts avec des ions trivalents (Fe3+ et Cr") ou irradies avec des rayons X a 77 K ou a 300 K. Quelques proprietes des defauts crCes par ces traitements sont decrites.

Structure and spectroscopy of Cr3+ defects in KMgF3, KZnF3, and CsCaF3 crystals. An ab initio model potential embedded cluster study

“…The second most abundant point defect is axially distorted along a [111] axis and is coupled to a nearest K + vacancy. Finally, the less probable C 4v site symmetry results from a distortion along the [100] axis and is expected to be associated to a nearest Mg 2+ vacancy [11,12,15,20]. The results we present here correspond to the calculation of the local structure parameters and spectroscopy of the cubic defects only.…”

“…The local structure of the three doped crystals, KMgF 3 :Cr 3+ [11,12], KZnF 3 :Cr 3+ [11,12,15], and CsCaF 3 :Cr 3+ [20], has been studied by means of ESR and EPR measurements. All the studies unanimously describe the existence of point defects with O h , C 3v , and C 2v site symmetries which result from different charge compensation mechanisms occurring as Cr 3+ substitutes for Mg 2+ , Zn 2+ , and Ca 2+ ions, respectively.…”

Ab initio model potential embedded-cluster study of the ground and lowest excited states of Cr3+ defects in the elpasolites Cs2NaYCl6 and Cs2NaYBr6

“…This effort still continues, involving more complex d 3 charged defects resulting from local charge compensation. [31][32][33][34][35][36] The investigations aim at measuring in detail the electronic spectra originating in the ground states ͑ground state absorption͒ and also in the excitated states ͑excited-state absorption and emission difference spectra͒, as well as their host variations, temperature dependences, pressure induced changes, etc. As a result of such a simultaneous effort of different experimental groups, a considerable amount of definite information has been accumulated, at a time that new questions have been raised and gaps of information have become apparent.…”

Theoretical investigation of local lattice structure of the tetragonal FeF5O cluster in KMgF3:Fe3+ crystal

“…In the case of Fe 3+ ions doped into KMgF 3 crystal, a tetragonal defect center has been observed by electron paramagnetic resonance (EPR) experiment [7,8] in addition to a K-vacancy site [3]. This tetragonal site is characteristic of a very large rank-2 axial zero-field splitting (ZFS) parameter (|b 0 2 | = 0.3572 cm −1 ) [7,8], several times greater in magnetic than those (|b 0 2 | = 0.04 − 0.08 cm −1 ) for M-vacancy sites in AMF 3 crystals [4,5]. This result has been assigned to an FeF 5 O configuration (see Fig.…”

“…In the last years much attention has been paid to the investigations of transition-metal (TM) ions doped into fluoroperovskite-type AMF 3 crystals (A represents an alkali metal and M represents an alkaline-earth metal ion) [1][2][3][4][5][6][7][8][9][10]. Magnetic impurity ions doped in the layered perovskite fluorides are expected to substitute for host cations and form the magnetic impurity center.…”