Low symmetry aspects in spectroscopic and magnetic susceptibility studies of Tb3+(4f8)in TbAlO3
来源期刊:JOURNAL OF RARE EARTHS2009年第4期
论文作者:P.Gnutek C.Rudowicz M.G.Brik
Key words:Tb3+ ions; ThAlO3; spectroscopy; crystal-field; magnetic susceptibility; low symmetry aspects; rare earths;
Abstract: The three sets of crystal field parameters (CFPs) obtained from spectroscopic and magnetic susceptibility studies of Th3+(4f8) ions in TbAlO3 by Gruber et al.(J.Lumin.128 (2008) 1271) were reanalyzed.These sets,fitted from experimental energy levels,are physically equivalent and correspond to specific choices of the axis system.Proper interpretation of experimental data for Tb3+ ions at monoclinic Cs symmetry sites in TbAlO3 crystal requires clarification of several intricate low symmetry aspects,namely,(a) three equivalent forms of monoclinic CF Hamiltonian,(b) relative orientation of the crystallographic axis system w.r.t,the symmetry-adapted axis system,(c) monoclinic standardization of CFPs,(d) distinction between the actual and apparent low symmetry effects exhibited by CFPs,and (e) nominal nature of all fitted CFP sets.For this purpose,modeling of CFPs for Th3+ in TbAlO3 was carried out using at the first stage only the Coulomb,i.e.point charge,contributions in the exchange charge model.The point charge model calculated CFPs disagree with the experimental CFPs,especially the rank k=6 CFPs.To explain this discrepancy and to verify the correctness of the theoretical CFP calculations additionally the superposition model was employed.The methods of analysis and modeling of CFP sets for monoclinic symmetry cases proposed here proved usefill for the studied case as well as might be used for other ion-host systems exhibiting monoclinic or triclirtic local site symmetry.Partial results for Th3+ ions in ThAlO3 were presented here,whereas detailed results were given in a follow-up paper.
P.Gnutek1,C.Rudowicz1,M.G.Brik2
(1.Modeling in Spectroscopy Group,Institute of Physics,West Pomeranian University of Technology,Szczecin,70-310,Poland;
2.Insitute of Physics,University of Tartu,51014 Tartu,Estonia)
Abstract:The three sets of crystal field parameters (CFPs) obtained from spectroscopic and magnetic susceptibility studies of Th3+(4f8) ions in TbAlO3 by Gruber et al.(J.Lumin.128 (2008) 1271) were reanalyzed.These sets,fitted from experimental energy levels,are physically equivalent and correspond to specific choices of the axis system.Proper interpretation of experimental data for Tb3+ ions at monoclinic Cs symmetry sites in TbAlO3 crystal requires clarification of several intricate low symmetry aspects,namely,(a) three equivalent forms of monoclinic CF Hamiltonian,(b) relative orientation of the crystallographic axis system w.r.t,the symmetry-adapted axis system,(c) monoclinic standardization of CFPs,(d) distinction between the actual and apparent low symmetry effects exhibited by CFPs,and (e) nominal nature of all fitted CFP sets.For this purpose,modeling of CFPs for Th3+ in TbAlO3 was carried out using at the first stage only the Coulomb,i.e.point charge,contributions in the exchange charge model.The point charge model calculated CFPs disagree with the experimental CFPs,especially the rank k=6 CFPs.To explain this discrepancy and to verify the correctness of the theoretical CFP calculations additionally the superposition model was employed.The methods of analysis and modeling of CFP sets for monoclinic symmetry cases proposed here proved usefill for the studied case as well as might be used for other ion-host systems exhibiting monoclinic or triclirtic local site symmetry.Partial results for Th3+ ions in ThAlO3 were presented here,whereas detailed results were given in a follow-up paper.
Key words:Tb3+ ions; ThAlO3; spectroscopy; crystal-field; magnetic susceptibility; low symmetry aspects; rare earths;
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