Hike Asatryan - Academia.edu (original) (raw)
Papers by Hike Asatryan
Applied Magnetic Resonance, 2005
We performed a simulation of the chemical fluctuation regions in the lead-magnesiumniobate-like r... more We performed a simulation of the chemical fluctuation regions in the lead-magnesiumniobate-like relaxors by growing Pb~NbyO. ceramics. The coexistence of PbxNbyO ~ clusters with different chemical composition that is inclusive of Nb 5+ as well as Nb 3+ ions was assumed. The existence of mobile polaronic pseudo-Jahn-Teller holes on the oxygen ions in different Pb~NbyO~ clusters has been suggested by the electron paramagnetic resonance (EPR) experiment. Here light-induced EPR and EPR motional averaging effects related with such polaronic holes have been manifested. The appearance of new paramagnetic centers (S = 5/2, 3/2, 1/2) related with Cr a § impurities at the Nb ~+ sites with trapped hole pairs (hole bipolarons), the charge compensation and the exchange effect have been proposed as explanation for the results of the EPR experiment. The charge-transfer vibronic excitons with O-Nb 5 § charge transfer were directly detected by photoluminescence studies. The R-line in the Cr 3+ impu¡ photoluminescence evidences the appearance of the Cr o+ ion in such matrices.
Physical Review B
The electronic structure of non-Kramers Tb 3+ centers in single crystals of yttrium aluminum garn... more The electronic structure of non-Kramers Tb 3+ centers in single crystals of yttrium aluminum garnet (YAG) was studied using a new-generation high-frequency magnetic resonance spectrometer that allows measurements of electron paramagnetic resonance (EPR), electron spin echo (ESE), the photon echo on hyperfine components of Stark levels in zero magnetic field, and optically detected magnetic resonance (ODMR). It was created on the basis of a highly stable microwave bridge operating in the near-terahertz region (0.094 or 0.130 THz), both in continuous-wave (cw) and pulse modes, a nonresonant system for supplying microwave power to a sample, and a cryogen-free magneto-optical cryostat. EPR, ESE, and cw measurements at two frequencies allowed us to reliably and with high accuracy determine the parameters of Tb 3+ centers that occupy yttrium dodecahedral positions in YAG: g || = 15.8 ± 0.2, g ⊥ ≈ 0 (|| corresponds to one of the 100 crystal axes), the zero-field splitting = 2.705 ± 0.005 cm −1 , and the hyperfine interaction constant A = 0.197 ± 0.005 cm −1 . In addition to the Tb 3+ centers in a regular environment, EPR spectra with lower intensity and a resolved hyperfine structure were found for at least three types of additional Tb 3+ centers. They have symmetry, g factors, and hyperfine interaction constants which are close to those of the main Tb 3+ centers but differ in the zero-field splitting parameters that strongly depend on the crystal field. They were ascribed to Tb 3+ centers with nearby antisite Y Al defects. Similarity with several types of Ce 3+ centers in YAG crystals, the types, and relative concentrations of antisite defects are discussed. For one of the additional Tb 3+ centers, splitting of the energy levels in the zero field turned out to be close to an energy of 94 GHz microwave quanta, and intense echo signals were observed in weak magnetic fields and in the zero field corresponding to the EPR transitions between the hyperfine components of the Tb 3+ spin levels. ODMR spectra of Tb 3+ centers in YAG crystals, containing Ce and Tb, were obtained by monitoring the intensity of the Ce 3+ luminescence, which implies the transfer of energy from Tb 3+ ions to Ce 3+ ions with conservation of spin. This result seems to be important, since these systems are of interest for quantum communication and computations. Taking into account that cerium does not have isotopes with a nuclear spin and that terbium has 100% 159 Tb having nuclear spin I = 3/2 and a sufficiently large nuclear magnetic moment, the Tb 3+ − Ce 3+ system in garnet crystals can be promising for coherent information processing. Tb 3+ ions can play a role of qubits and Ce 3+ ion with a lifetime of about 50 ns, and almost unity quantum efficiency of optical transitions can be used as a single-ion readout arrangement. The prospects for using this system as hardware for quantum communication and computations are discussed.
physica status solidi (c)
ABSTRACT We report the study of the polarized optical absorption, the near-infrared luminescence ... more ABSTRACT We report the study of the polarized optical absorption, the near-infrared luminescence and the luminescence excitation spectra of the proper ferroelastic K3Na(CrO4)2 crystals doped with MnO42– ions. It is obtained from the luminescence and the d-d absorption spectra that the 3d1 electronic ground (2E) and excited (2T2) states of MnO42– are split by the monoclinic crystal field of the host lattice at T < 230 K. The well-resolved vibronic progressions in the luminescence spectra are ascribed to a strong coupling with a MnO42– bending ν2 = 335 cm–1 mode. The spectral dependence of the linear polarization degree ρ (ω) of the charge-tranfer absorption for E ‖ c and E ‖ b polarization reveals a clear periodic structure due to interaction of local electronic states with a ν1 = 816 cm−1 local mode. The first EPR spectrum of the Mn6+ paramagnetic center in the K3Na(CrO4)2: MnO42– crystal is studied. The local transition due to a local configuration instability of vibronic origin at low temperature T ≤ 18 K is detected and identified. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Applied Physics Letters
ABSTRACT
Materials Science Forum, 1997
International Journal of Modern Physics: Conference Series, 2012
The results of EPR investigations of the laser crystals and scintillators are presented, in parti... more The results of EPR investigations of the laser crystals and scintillators are presented, in particular, Y 3 Al 5 O 12: Dy 3+, Y 3 Al 5 O 12: Er 3+, ( Y 1-x Lu x)3 Al 5 O 12: Er 3+, YAlO 3: Er 3+, Ce 3+, Nd 3+ and Tm 3+, Y (1- x ) Lu x AlO 3 : Ce 3+, PbGa 2 S 4 : Dy 3+, Nd 3+ and Ce 3+. EPR signals of Er 3+, Ce 3+, Nd 3+ and Tm 3+ ions in YAlO 3, as well as of Dy 3+, Nd 3+ and Ce 3+ in lead thiogallate single crystals are detected and analyzed for the first time. The main values of g tensors and hyperfine interaction constants for Er 3+, Tm 3+, Nd 3+ and Dy 3+ odd isotopes are determined. In compositionally disordered compounds YLuAG and YLuAP several new paramagnetic Er 3+ and Ce 3+ centers are observed in comparison with YAG and YAP . These centers appear as a result of the changes in the crystal field symmetry and magnitude due to the isomorphic substitution of Lu 3+ for Y 3+ in the yttrium sublattice. The origin of these new paramagnetic centers is established and their formation...
physica status solidi (b), 1988
ABSTRACT ESR of Mo3+ ions in mixed single crystals of yttrium–scandium–aluminium garnets Y3Al2−xS... more ABSTRACT ESR of Mo3+ ions in mixed single crystals of yttrium–scandium–aluminium garnets Y3Al2−xScx. Al3O12, where 0 ≦ x ≦ 2 is investigated. Several new centers of Mo3+ differing from those for Y3Al5O12 single crystals are observed due to changes of symmetry and crystal field parameters associated with isomorphous substitution of octahedrally coordinated Al3+ (a) by those of Sc3+ in the third coordination sphere. Symmetry, nearest coordination, and spin–Hamiltonian parameters are estimated concerning with all Mo3+ centers in Y3Al2−xScxAl3O12 crystals for x < 0.15. It is found that in Y3Sc2Al3O12 (x = 2) the Sc3+ ions substitute also Y3+ at dodecahedral sites. [Russian Text Ignored].
Solid State Communications, 1997
EPR spectra of Er3+, Nd3+ and Ce3+ ions in YAlO3 lattice have been studied. These spectra can be ... more EPR spectra of Er3+, Nd3+ and Ce3+ ions in YAlO3 lattice have been studied. These spectra can be described by spin Hamiltonian with an effective spin S = 12 and rhombohedric symmetry. The g factors as well as the constants of hyperfine interaction of Nd3+ and Er3+ were obtained. It was stated that all the resonances which are upon the
Physics of the Solid State, 2005
ABSTRACT Simulation of the chemical fluctuation regions in PMN-like relaxors through growth of th... more ABSTRACT Simulation of the chemical fluctuation regions in PMN-like relaxors through growth of the PbxNbyOz eramics was performed. Different PbxNbyOz clusters (chemically and structurally) coexist in such ceramics. Hole polaron and bipolaron (Cr3+-two polaronic-hole) paramagnetic complexes were considered for explanation of the EPR spectra in PbxNbyOz ceramics. Dynamical averaging, light-induced effects, and significant effects of reduction treatment giving the coexistence of Nb5+ and Nb3+ ions, as well as of a strong internal magnetic field, were discovered in this ceramics. The latter could be related to antiferromagnetic phase realization in PbxNbyOz clusters containing a sufficiently high concentration of magnetic Nb3+ host lattice ions. Such a situation leads to antiferromagnetic resonance on Nb3+ ions, as well as to EPR of Cr3+-related paramagnetic complexes in a Nb3+-induced internal magnetic field. Charge transfer vibronic excitons (CTVE) in free and in CTVE phase states were detected in PbxNbyOz ceramics by photoluminescence studies.
Physics of the Solid State, 2003
ABSTRACT The results of EPR studies of Ce3+ ions incorporated into single crystals of mixed yttri... more ABSTRACT The results of EPR studies of Ce3+ ions incorporated into single crystals of mixed yttrium-lutecium orthoaluminates Y1−x LuxAlO3 (YLuAP, x=0.1, 0.3) are reported. In compositionally disordered YLuAP compounds, in comparison to YAlO3, new paramagnetic Ce3+ centers are found. These centers are caused by the changes in symmetry and in the crystal field magnitude due to the isomorphic substitution of Y3+ ions by Lu3+ in the yttrium sublattice of orthoaluminates. It is shown that the formation of 27 different types of centers is possible in YLuAP with variation of the Lu content. The probabilities of formation of new paramagnetic centers are calculated.
physica status solidi (b), 1980
ABSTRACT ESR of Mo3+ ions and NMR of 27Al nuclei is investigated in mixed single crystals of yttr... more ABSTRACT ESR of Mo3+ ions and NMR of 27Al nuclei is investigated in mixed single crystals of yttrium-lutetium-aluminum garnets (Y1−xLux)3Al5O12, where O ≦ x ≦ 1. Several new centres of Mo3+ and 27Al compared with Y3Al5O12 and Lu3Al5O12 single crystals are revealed associated with symmetry and crystalline field parameter changes at isomorphous substitution of Y3+ ions in the rare-earth sublattice of the garnet by those of Lu3+. Symmetry, nearest coordination, and parameters of spin-Hamiltonians are estimated concerning all of Mo3+ and 27Al centres in (Y1−xLux)3Al5O12, at x < 0.15. [Russian Text Ignored].
physica status solidi (b), 1980
... Mirzakhanyan, AA, Petrosyan, AK and Asatryan, HR (1981), Angular Dependence of the Interdoubl... more ... Mirzakhanyan, AA, Petrosyan, AK and Asatryan, HR (1981), Angular Dependence of the Interdoublet EPR Spectrum of Fe 3+ and Mn 2+ in Pb 5 Ge 3 O 11 Single ... Issue published online: 9 FEB 2006; Article first published online: 9 FEB 2006; Manuscript Received: 11 MAR 1981. ...
physica status solidi (b), 1986
ABSTRACT Single crystals of yttrium aluminium garnet doped with zirconium ions (Y3Al5O12:Zr, YAG:... more ABSTRACT Single crystals of yttrium aluminium garnet doped with zirconium ions (Y3Al5O12:Zr, YAG:Zr) are grown from the melt and their optical and ESR absorption spectra are investigated. It is established that the color centers and paramagnetic centers have an identical nature being caused by Zr3+ ions in dodechahedrical sites of the garnet lattice. The experimental results are interpreted in the approximation of crystal field and molecular orbital theories. [Russian Text Ignored].
Physica Status Solidi (a), 1996
ABSTRACT An EPR investigation of rare earth trace impurities in PbWO4 single crystals was carried... more ABSTRACT An EPR investigation of rare earth trace impurities in PbWO4 single crystals was carried out at 4.2 < T < 300 K. The Nd3+ and Ce3+ ions were identified, being described by an axial spin Hamiltonian with an effective spin. The g-factors of Nd3+ and Ce3+ as well as the constants of hyperfine interaction of Nd3+ were obtained.
Ferroelectrics, 2004
ABSTRACT The simulation of chemical fluctuation regions in the PMN-like relaxors by growth of the... more ABSTRACT The simulation of chemical fluctuation regions in the PMN-like relaxors by growth of the PbxNbyOz—ceramics was performed. The coexistence of PbxNbyOz—clusters with different chemical composition inclusive Nb as well as Nb ions was assumed. An existence of paramagnetic Cr ions on Nb sites with charge compensation by two-oxygen hole bi-polarons with intermediate radius and in singlet states was suggested on the basis of EPR-experiment. A dissociation of such a bi-polaron with temperature via crossover with large radius bi-polaron produces finally the EPR-active free holes. They take part in spectrum motional averaging due to hopping transitions between different PbxNbyOz—clusters. New light induced EPR-lines were detected. This new lines are connected with two origins. First, it is effect of light-induced complexes which are appeared due to trapping of a space charge on the core-like Fe ions located on Nb sites in PbxNb yOz—clusters. Second, it is effect of Ti ions on Pb sites which are appeared under successive photo-recharging of non-paramagnetic Ti Pb2+ and paramagnetic Ti Pb2+ ions in accord with photo-chemical recharging transformation: Ti Pb2+ ↞ Ti Pb2+ ↞ Ti Pb2+. Charge transfer vibronic excitons with O → Nb charge transfer was directly detected by photoluminescence studies. R-line Cr impurity photoluminescence manifestation independently confirms the Cr ion appearance on Nb ion sites in such matrices.
Ferroelectrics, 2007
Temperature dependences of EPR spectrum for Mn paramagnetic center embodied in MnO4 molecular imp... more Temperature dependences of EPR spectrum for Mn paramagnetic center embodied in MnO4 molecular impurity ion in proper ferroelastric K3Na(CrO4)2 were studied. Local transition due to local electron-lattice instability appearing at low temperature region T ≤ 18 K has been detected and identified for this system in the first time. Model of the phenomenon is based on the transformation of Jahn-Teller effect to pseudo-Jahn-Teller effect with its the following complete suppressing under the action of ferroelastic order parameter increase at low temperatures.
International Journal of Modern Physics: Conference Series, 2012
The results of EPR investigations of the laser crystals and scintillators are presented, in parti... more The results of EPR investigations of the laser crystals and scintillators are presented, in particular, Y 3 Al 5 O 12: Dy 3+, Y 3 Al 5 O 12: Er 3+, ( Y 1-x Lu x)3 Al 5 O 12: Er 3+, YAlO 3: Er 3+, Ce 3+, Nd 3+ and Tm 3+, Y (1- x ) Lu x AlO 3 : Ce 3+, PbGa 2 S 4 : Dy 3+, Nd 3+ and Ce 3+. EPR signals of Er 3+, Ce 3+, Nd 3+ and Tm 3+ ions in YAlO 3, as well as of Dy 3+, Nd 3+ and Ce 3+ in lead thiogallate single crystals are detected and analyzed for the first time. The main values of g tensors and hyperfine interaction constants for Er 3+, Tm 3+, Nd 3+ and Dy 3+ odd isotopes are determined. In compositionally disordered compounds YLuAG and YLuAP several new paramagnetic Er 3+ and Ce 3+ centers are observed in comparison with YAG and YAP . These centers appear as a result of the changes in the crystal field symmetry and magnitude due to the isomorphic substitution of Lu 3+ for Y 3+ in the yttrium sublattice. The origin of these new paramagnetic centers is established and their formation...
Applied Magnetic Resonance, 2005
We performed a simulation of the chemical fluctuation regions in the lead-magnesiumniobate-like r... more We performed a simulation of the chemical fluctuation regions in the lead-magnesiumniobate-like relaxors by growing Pb~NbyO. ceramics. The coexistence of PbxNbyO ~ clusters with different chemical composition that is inclusive of Nb 5+ as well as Nb 3+ ions was assumed. The existence of mobile polaronic pseudo-Jahn-Teller holes on the oxygen ions in different Pb~NbyO~ clusters has been suggested by the electron paramagnetic resonance (EPR) experiment. Here light-induced EPR and EPR motional averaging effects related with such polaronic holes have been manifested. The appearance of new paramagnetic centers (S = 5/2, 3/2, 1/2) related with Cr a § impurities at the Nb ~+ sites with trapped hole pairs (hole bipolarons), the charge compensation and the exchange effect have been proposed as explanation for the results of the EPR experiment. The charge-transfer vibronic excitons with O-Nb 5 § charge transfer were directly detected by photoluminescence studies. The R-line in the Cr 3+ impu¡ photoluminescence evidences the appearance of the Cr o+ ion in such matrices.
Physical Review B
The electronic structure of non-Kramers Tb 3+ centers in single crystals of yttrium aluminum garn... more The electronic structure of non-Kramers Tb 3+ centers in single crystals of yttrium aluminum garnet (YAG) was studied using a new-generation high-frequency magnetic resonance spectrometer that allows measurements of electron paramagnetic resonance (EPR), electron spin echo (ESE), the photon echo on hyperfine components of Stark levels in zero magnetic field, and optically detected magnetic resonance (ODMR). It was created on the basis of a highly stable microwave bridge operating in the near-terahertz region (0.094 or 0.130 THz), both in continuous-wave (cw) and pulse modes, a nonresonant system for supplying microwave power to a sample, and a cryogen-free magneto-optical cryostat. EPR, ESE, and cw measurements at two frequencies allowed us to reliably and with high accuracy determine the parameters of Tb 3+ centers that occupy yttrium dodecahedral positions in YAG: g || = 15.8 ± 0.2, g ⊥ ≈ 0 (|| corresponds to one of the 100 crystal axes), the zero-field splitting = 2.705 ± 0.005 cm −1 , and the hyperfine interaction constant A = 0.197 ± 0.005 cm −1 . In addition to the Tb 3+ centers in a regular environment, EPR spectra with lower intensity and a resolved hyperfine structure were found for at least three types of additional Tb 3+ centers. They have symmetry, g factors, and hyperfine interaction constants which are close to those of the main Tb 3+ centers but differ in the zero-field splitting parameters that strongly depend on the crystal field. They were ascribed to Tb 3+ centers with nearby antisite Y Al defects. Similarity with several types of Ce 3+ centers in YAG crystals, the types, and relative concentrations of antisite defects are discussed. For one of the additional Tb 3+ centers, splitting of the energy levels in the zero field turned out to be close to an energy of 94 GHz microwave quanta, and intense echo signals were observed in weak magnetic fields and in the zero field corresponding to the EPR transitions between the hyperfine components of the Tb 3+ spin levels. ODMR spectra of Tb 3+ centers in YAG crystals, containing Ce and Tb, were obtained by monitoring the intensity of the Ce 3+ luminescence, which implies the transfer of energy from Tb 3+ ions to Ce 3+ ions with conservation of spin. This result seems to be important, since these systems are of interest for quantum communication and computations. Taking into account that cerium does not have isotopes with a nuclear spin and that terbium has 100% 159 Tb having nuclear spin I = 3/2 and a sufficiently large nuclear magnetic moment, the Tb 3+ − Ce 3+ system in garnet crystals can be promising for coherent information processing. Tb 3+ ions can play a role of qubits and Ce 3+ ion with a lifetime of about 50 ns, and almost unity quantum efficiency of optical transitions can be used as a single-ion readout arrangement. The prospects for using this system as hardware for quantum communication and computations are discussed.
physica status solidi (c)
ABSTRACT We report the study of the polarized optical absorption, the near-infrared luminescence ... more ABSTRACT We report the study of the polarized optical absorption, the near-infrared luminescence and the luminescence excitation spectra of the proper ferroelastic K3Na(CrO4)2 crystals doped with MnO42– ions. It is obtained from the luminescence and the d-d absorption spectra that the 3d1 electronic ground (2E) and excited (2T2) states of MnO42– are split by the monoclinic crystal field of the host lattice at T < 230 K. The well-resolved vibronic progressions in the luminescence spectra are ascribed to a strong coupling with a MnO42– bending ν2 = 335 cm–1 mode. The spectral dependence of the linear polarization degree ρ (ω) of the charge-tranfer absorption for E ‖ c and E ‖ b polarization reveals a clear periodic structure due to interaction of local electronic states with a ν1 = 816 cm−1 local mode. The first EPR spectrum of the Mn6+ paramagnetic center in the K3Na(CrO4)2: MnO42– crystal is studied. The local transition due to a local configuration instability of vibronic origin at low temperature T ≤ 18 K is detected and identified. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Applied Physics Letters
ABSTRACT
Materials Science Forum, 1997
International Journal of Modern Physics: Conference Series, 2012
The results of EPR investigations of the laser crystals and scintillators are presented, in parti... more The results of EPR investigations of the laser crystals and scintillators are presented, in particular, Y 3 Al 5 O 12: Dy 3+, Y 3 Al 5 O 12: Er 3+, ( Y 1-x Lu x)3 Al 5 O 12: Er 3+, YAlO 3: Er 3+, Ce 3+, Nd 3+ and Tm 3+, Y (1- x ) Lu x AlO 3 : Ce 3+, PbGa 2 S 4 : Dy 3+, Nd 3+ and Ce 3+. EPR signals of Er 3+, Ce 3+, Nd 3+ and Tm 3+ ions in YAlO 3, as well as of Dy 3+, Nd 3+ and Ce 3+ in lead thiogallate single crystals are detected and analyzed for the first time. The main values of g tensors and hyperfine interaction constants for Er 3+, Tm 3+, Nd 3+ and Dy 3+ odd isotopes are determined. In compositionally disordered compounds YLuAG and YLuAP several new paramagnetic Er 3+ and Ce 3+ centers are observed in comparison with YAG and YAP . These centers appear as a result of the changes in the crystal field symmetry and magnitude due to the isomorphic substitution of Lu 3+ for Y 3+ in the yttrium sublattice. The origin of these new paramagnetic centers is established and their formation...
physica status solidi (b), 1988
ABSTRACT ESR of Mo3+ ions in mixed single crystals of yttrium–scandium–aluminium garnets Y3Al2−xS... more ABSTRACT ESR of Mo3+ ions in mixed single crystals of yttrium–scandium–aluminium garnets Y3Al2−xScx. Al3O12, where 0 ≦ x ≦ 2 is investigated. Several new centers of Mo3+ differing from those for Y3Al5O12 single crystals are observed due to changes of symmetry and crystal field parameters associated with isomorphous substitution of octahedrally coordinated Al3+ (a) by those of Sc3+ in the third coordination sphere. Symmetry, nearest coordination, and spin–Hamiltonian parameters are estimated concerning with all Mo3+ centers in Y3Al2−xScxAl3O12 crystals for x < 0.15. It is found that in Y3Sc2Al3O12 (x = 2) the Sc3+ ions substitute also Y3+ at dodecahedral sites. [Russian Text Ignored].
Solid State Communications, 1997
EPR spectra of Er3+, Nd3+ and Ce3+ ions in YAlO3 lattice have been studied. These spectra can be ... more EPR spectra of Er3+, Nd3+ and Ce3+ ions in YAlO3 lattice have been studied. These spectra can be described by spin Hamiltonian with an effective spin S = 12 and rhombohedric symmetry. The g factors as well as the constants of hyperfine interaction of Nd3+ and Er3+ were obtained. It was stated that all the resonances which are upon the
Physics of the Solid State, 2005
ABSTRACT Simulation of the chemical fluctuation regions in PMN-like relaxors through growth of th... more ABSTRACT Simulation of the chemical fluctuation regions in PMN-like relaxors through growth of the PbxNbyOz eramics was performed. Different PbxNbyOz clusters (chemically and structurally) coexist in such ceramics. Hole polaron and bipolaron (Cr3+-two polaronic-hole) paramagnetic complexes were considered for explanation of the EPR spectra in PbxNbyOz ceramics. Dynamical averaging, light-induced effects, and significant effects of reduction treatment giving the coexistence of Nb5+ and Nb3+ ions, as well as of a strong internal magnetic field, were discovered in this ceramics. The latter could be related to antiferromagnetic phase realization in PbxNbyOz clusters containing a sufficiently high concentration of magnetic Nb3+ host lattice ions. Such a situation leads to antiferromagnetic resonance on Nb3+ ions, as well as to EPR of Cr3+-related paramagnetic complexes in a Nb3+-induced internal magnetic field. Charge transfer vibronic excitons (CTVE) in free and in CTVE phase states were detected in PbxNbyOz ceramics by photoluminescence studies.
Physics of the Solid State, 2003
ABSTRACT The results of EPR studies of Ce3+ ions incorporated into single crystals of mixed yttri... more ABSTRACT The results of EPR studies of Ce3+ ions incorporated into single crystals of mixed yttrium-lutecium orthoaluminates Y1−x LuxAlO3 (YLuAP, x=0.1, 0.3) are reported. In compositionally disordered YLuAP compounds, in comparison to YAlO3, new paramagnetic Ce3+ centers are found. These centers are caused by the changes in symmetry and in the crystal field magnitude due to the isomorphic substitution of Y3+ ions by Lu3+ in the yttrium sublattice of orthoaluminates. It is shown that the formation of 27 different types of centers is possible in YLuAP with variation of the Lu content. The probabilities of formation of new paramagnetic centers are calculated.
physica status solidi (b), 1980
ABSTRACT ESR of Mo3+ ions and NMR of 27Al nuclei is investigated in mixed single crystals of yttr... more ABSTRACT ESR of Mo3+ ions and NMR of 27Al nuclei is investigated in mixed single crystals of yttrium-lutetium-aluminum garnets (Y1−xLux)3Al5O12, where O ≦ x ≦ 1. Several new centres of Mo3+ and 27Al compared with Y3Al5O12 and Lu3Al5O12 single crystals are revealed associated with symmetry and crystalline field parameter changes at isomorphous substitution of Y3+ ions in the rare-earth sublattice of the garnet by those of Lu3+. Symmetry, nearest coordination, and parameters of spin-Hamiltonians are estimated concerning all of Mo3+ and 27Al centres in (Y1−xLux)3Al5O12, at x < 0.15. [Russian Text Ignored].
physica status solidi (b), 1980
... Mirzakhanyan, AA, Petrosyan, AK and Asatryan, HR (1981), Angular Dependence of the Interdoubl... more ... Mirzakhanyan, AA, Petrosyan, AK and Asatryan, HR (1981), Angular Dependence of the Interdoublet EPR Spectrum of Fe 3+ and Mn 2+ in Pb 5 Ge 3 O 11 Single ... Issue published online: 9 FEB 2006; Article first published online: 9 FEB 2006; Manuscript Received: 11 MAR 1981. ...
physica status solidi (b), 1986
ABSTRACT Single crystals of yttrium aluminium garnet doped with zirconium ions (Y3Al5O12:Zr, YAG:... more ABSTRACT Single crystals of yttrium aluminium garnet doped with zirconium ions (Y3Al5O12:Zr, YAG:Zr) are grown from the melt and their optical and ESR absorption spectra are investigated. It is established that the color centers and paramagnetic centers have an identical nature being caused by Zr3+ ions in dodechahedrical sites of the garnet lattice. The experimental results are interpreted in the approximation of crystal field and molecular orbital theories. [Russian Text Ignored].
Physica Status Solidi (a), 1996
ABSTRACT An EPR investigation of rare earth trace impurities in PbWO4 single crystals was carried... more ABSTRACT An EPR investigation of rare earth trace impurities in PbWO4 single crystals was carried out at 4.2 < T < 300 K. The Nd3+ and Ce3+ ions were identified, being described by an axial spin Hamiltonian with an effective spin. The g-factors of Nd3+ and Ce3+ as well as the constants of hyperfine interaction of Nd3+ were obtained.
Ferroelectrics, 2004
ABSTRACT The simulation of chemical fluctuation regions in the PMN-like relaxors by growth of the... more ABSTRACT The simulation of chemical fluctuation regions in the PMN-like relaxors by growth of the PbxNbyOz—ceramics was performed. The coexistence of PbxNbyOz—clusters with different chemical composition inclusive Nb as well as Nb ions was assumed. An existence of paramagnetic Cr ions on Nb sites with charge compensation by two-oxygen hole bi-polarons with intermediate radius and in singlet states was suggested on the basis of EPR-experiment. A dissociation of such a bi-polaron with temperature via crossover with large radius bi-polaron produces finally the EPR-active free holes. They take part in spectrum motional averaging due to hopping transitions between different PbxNbyOz—clusters. New light induced EPR-lines were detected. This new lines are connected with two origins. First, it is effect of light-induced complexes which are appeared due to trapping of a space charge on the core-like Fe ions located on Nb sites in PbxNb yOz—clusters. Second, it is effect of Ti ions on Pb sites which are appeared under successive photo-recharging of non-paramagnetic Ti Pb2+ and paramagnetic Ti Pb2+ ions in accord with photo-chemical recharging transformation: Ti Pb2+ ↞ Ti Pb2+ ↞ Ti Pb2+. Charge transfer vibronic excitons with O → Nb charge transfer was directly detected by photoluminescence studies. R-line Cr impurity photoluminescence manifestation independently confirms the Cr ion appearance on Nb ion sites in such matrices.
Ferroelectrics, 2007
Temperature dependences of EPR spectrum for Mn paramagnetic center embodied in MnO4 molecular imp... more Temperature dependences of EPR spectrum for Mn paramagnetic center embodied in MnO4 molecular impurity ion in proper ferroelastric K3Na(CrO4)2 were studied. Local transition due to local electron-lattice instability appearing at low temperature region T ≤ 18 K has been detected and identified for this system in the first time. Model of the phenomenon is based on the transformation of Jahn-Teller effect to pseudo-Jahn-Teller effect with its the following complete suppressing under the action of ferroelastic order parameter increase at low temperatures.
International Journal of Modern Physics: Conference Series, 2012
The results of EPR investigations of the laser crystals and scintillators are presented, in parti... more The results of EPR investigations of the laser crystals and scintillators are presented, in particular, Y 3 Al 5 O 12: Dy 3+, Y 3 Al 5 O 12: Er 3+, ( Y 1-x Lu x)3 Al 5 O 12: Er 3+, YAlO 3: Er 3+, Ce 3+, Nd 3+ and Tm 3+, Y (1- x ) Lu x AlO 3 : Ce 3+, PbGa 2 S 4 : Dy 3+, Nd 3+ and Ce 3+. EPR signals of Er 3+, Ce 3+, Nd 3+ and Tm 3+ ions in YAlO 3, as well as of Dy 3+, Nd 3+ and Ce 3+ in lead thiogallate single crystals are detected and analyzed for the first time. The main values of g tensors and hyperfine interaction constants for Er 3+, Tm 3+, Nd 3+ and Dy 3+ odd isotopes are determined. In compositionally disordered compounds YLuAG and YLuAP several new paramagnetic Er 3+ and Ce 3+ centers are observed in comparison with YAG and YAP . These centers appear as a result of the changes in the crystal field symmetry and magnitude due to the isomorphic substitution of Lu 3+ for Y 3+ in the yttrium sublattice. The origin of these new paramagnetic centers is established and their formation...