Tae Ho Yeom

Electron Magnetic Resonance of Eu 2+ in SrCl 2 :Eu Single Crystal

The electron paramagnetic resonance (EPR) of the Eu 2+ + ion in SrCl 2 :Eu single crystal has been investigated using an X-band spectrometer. The angular dependence of magnetic resonance positions for the Eu 2+ + impurity ion in the crystallographic aa-plane is analyzed with effective spin-Hamiltonian. The EPR spectra of the isolated Eu 2+ + center merged to each other. The hyperfine splitting of the isolated Eu 2+ + center due to the 151Eu nucleus is approximately 35 G. Three kinds of Eu 2+ + centers except the isolated Eu 2+ + center, Eu 2+ + pairs, Eu 2+ + triples, and other Eu 2+ + clusters, are split from the fitting of the integrated experimental spectrum with the Gaussian curve. The calculated spectroscopic splitting parameters of the Eu 2+ + pairs, Eu 2+ + triples, and other Eu 2+ + clusters in SrCl 2 :Eu crystal are g 1 = 2.06, g 2 = 1.94, and g 3 = 1.93, respectively.

Temperature Dependence of Mn 2+ Paramagnetic Ion in a Stoichiometric LiNbO₃ Single Crystal

Electron paramagnetic resonance (EPR) spectra of Mn2+ impurity ion in Stoichiometric LiNbO₃ single crystal (SLN) was investigated with an X-band EPR spectrometer in the temperature range of 3 K~296 K. The intensity of EPR spectrum of Mn²+ ion was increased to 20 K and decreased again below 20 K as the temperature decreases. The zero-field splitting parameter D decreased as the temperature increases. It was suggested that Mn²+ ion substitute for Nb5+ ion instead of Li+ ion. No changes for hyperfine interaction of Mn²+ ion was obtained in the temperature range of 3 K~296 K.

Characterization of Cu2+ Impurity Ion in K₂SnCl6:Cu Single Crystal

K2SnCl6 single crystals doped with Cu were grown by the evaporation of saturated solution. The electron magnetic resonance (EMR) of the Cu ion in the crystal has been investigated by using an X-band spectrometer. The rotation pattern in the crystallographic plane together with spin Hamiltonian parameters of Cu ion in K2SnCl6:Cu single crystal shows that the local site symmetry of the Cu 2+ ion is cubic at room temperature. The calculated spectroscopic splitting factor g of Cu impurity ion is 2.1908(±0.0007). The hyperfine constants of Cu impurity ion due to the Cu and Cu isotopes in K2SnCl6:Cu crystal are 0.83(±0.01)×10 −4 cm and 0.89(±0.01)×10 cm, respectively. It turns out that the Cu ion substitutes for the K ion without any nearby charge compensation.

Ground State Energy of Gd 3+ Paramagnetic Ion in PbWO 4 : Gd Single Crystal

:Gdsingle crystal. The calculated energy differences for |± 7/2>↔|± 5/2>, |± 5/2>↔|± 3/2>, and |± 3/2>↔|± 1/2> transitions were6.9574 GHz, 6.9219 GHz, and 15.8704 GHz, respectively when the applied magnetic field is zero. The calculated energy leveldiagrams were different for different directions of applied magnetic field. For B // a- and c-axis, the energy level diagrams arecalculated and discussed.Keywords : PbWO

Nuclear Magnetic Resonance Study of 23 Na in NaMgCl 3 Single Crystal

We have investigated nuclear magnetic resonance of Na nucleus in NaMgCl3 single crystal in the temperature range 200 K~410 K using FT-NMR spectrometer. The spin-lattice relaxation times T1 of Na nucleus residing at cubic symmetry in the host crystal was measured as a function of temperature. The T1 of Na nucleus decreased with increasing temperature. The nuclear spin-lattice relaxation rate 1/T1 of Na in NaMgCl3 single crystal was proportional to the temperature T. This behavior is explained with the characteristic feature of the direct process between the nuclear spins and single phonon, 1/T1 being proportional to the absolute temperature. The activation energy calculated was E a = 4.82 J/mol.

Nuclear Magnetic Resonance Study of 23 Na Nucleus in NaBrO₃ Single Crystal

The nuclear magnetic resonance of the 23 Na nucleus in a NaBrO₃ single crystal was investigated at the temperature range of 200 K~410 K. The tendencies of temperature dependence of the nuclear quadrupole coupling for the two magnetically inequivalent Na(I) and Na(II) centers are found to be opposite to each other. The nuclear spin-lattice relaxation mechanism of 23 Na in the NaBrO₃ crystal is investigated, and the result revealed that the Raman process is dominant in the temperature range investigated. The relaxation process of the 23 Na nuclear spins was well described by a single exponential function in time. The T 1 values of the 23 Na nuclei in the NaBrO₃ single crystal decreased with increasing temperature. The calculated activation energy for the 23Na is 0.032 ± 0.002 eV.

Energy Level Calculation of Fe 3+ Paramagnetic Impurity Ion in a LiTaO 3 Single Crystal

Ground state energy levels of the Fe paramagnetic impurity ion in stoichiometric LiTaO3 and in congruent LiTaO3 single crystals were calculated with electron paramagnetic resonance constants. Energy levels between six energy levels were obtained with spectroscopic splitting parameter g and zero field splitting constant D for Fe ion. The energy diagrams of Fe ion were different from different magnetic field directions ([100], [001], [111]) when magnetic field increases. The calculated ZFS energies of Fe ion in stoichiometric and congruent LiTaO3 single crystals for |± 5/2> ↔ |± 3/2> and |± 3/2> ↔ |± 1/2> transitions were 12.300 GHz and 6.150 GHz, and 59.358 GHz and 29.679 GHz, respectively. It turns out that energy levels of Fe paramagnetic impurity in LiTaO3 crystal are different from different crystal growing condition.

Activation Energy of 69 Ga, 71 Ga, and 75 As Nuclei in GaAs:Mn 2+ Single Crystal

The spin?lattice relaxation time, T1, for 69 Ga, 71 Ga, and 75 As nuclei in GaAs:Mn2+ single crystals was measured as a function of temperature. The values of T1 for 69 Ga, 71 Ga, and 75 As nuclei were found to decrease with increasing temperature. The T1 values in GaAs:Mn 2+ crystal are similar to those in pure GaAs crystal. The calculated activation energies for the 69 Ga, 71 Ga, and 75 As nuclei are 4.34, 4.07, and 3.99 kJ/mol. It turns out that the paramagnetic impurity effect of Mn 2+ ion doped in GaAs single crystal was not strong on the spin-lattice relaxation time.

Study of nuclear quadrupole interactions and quadrupole Raman processes of 69Ga and 71Ga in a β-Ga2O3:Cr3+ single crystal

Nuclear magnetic resonance (NMR) data and the spin-lattice relaxation times, T(1), of (69)Ga and (71)Ga nuclei in a beta-Ga(2)O(3):Cr(3+) single crystal were obtained using FT NMR spectrometry. Four sets of NMR spectra for (69)Ga (I=3/2) and (71)Ga (I=3/2) were obtained in the crystallographic planes. The (69)Ga and (71)Ga nuclei each had two chemically inequivalent Ga(I) and Ga(II) centers. Each of the (69)Ga and (71)Ga isotopes yielded two different central NMR resonance lines originating from Ga(I) and Ga(II) sites. The nuclear quadrupole coupling constants and asymmetry parameters of (69)Ga(I), (69)Ga(II), (71)Ga(I), and (71)Ga(II) centers in a beta-Ga(2)O(3):Cr(3+) crystal were obtained. Analysis of the EFG tensor principal axes (PAs) for Ga nuclei and the ZFS tensor PAs for the Cr(3+) ion confirmed that the Cr(3+) paramagnetic impurity ion substitutes for the Ga(3+) ion in the oxygen octahedron. In addition, the temperature dependencies of the (69)Ga and (71)Ga relaxation rates were consistent with Raman processes, as T(1)(-1) is proportional to T(2). Even though the Cr(3+) impurities are paramagnetic, the relaxations were dominated by electric quadrupole interactions of the nuclear spins in the temperature range investigated.