Proof of the Acceptor State of the Trigonal Iron-Boron Pair in Silicon by Electron Paramagnetic Resonance Measurements

1992 ◽  
Vol 262 ◽  
Author(s):  
W. Gehlhoff ◽  
U. Rehse
Keyword(s):  
Zero Field ◽  
Electrical Measurements ◽  
Zero Field Splitting ◽  
Acceptor State ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Zero Field Splitting Parameter ◽  
Splitting Parameter ◽  
First Time ◽  
Electron Paramagnetic

ABSTRACTFor the first time the acceptor state of iron-boron pairs the occurence of which are suggested by electrical measurements and theoretical considerations is directly proved by EPR measurements. The corresponding EPR spectrum is observed upon suitable illumination of samples which have been co-doped with boron and iron. It shows trigonal symmetry, and the fine-structure pattern can be described with the spin S = l, the g-values gi ∼ 2.1345±0.0001, gi = 2.1345±0.0004 and the zero-field splitting parameter |D| = (1.418±0.001) cm−1.

scholarly journals Electron Paramagnetic Resonance and DTA Investigation of Cr3+ in Tris(guanidinium) Hexafluoroaluminate Single Crystals

1998 ◽  
Vol 53 (5) ◽  
pp. 245-250
Author(s):  
T. Lakshmi Kasturi ◽  
V. G. Krishnan
Keyword(s):  
Phase Transition ◽  
Electron Paramagnetic Resonance ◽  
Single Crystals ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Paramagnetic Resonance ◽  
Aluminum Salts ◽  
Zero Field Splitting Parameter ◽  
Splitting Parameter ◽  
Electron Paramagnetic

Abstract Electron Paramagnetic Resonance (EPR) studies of Cr 3+ in single crystals of tris(guanidinium) hexafluoroaluminate, [C(NH2)3]3 AlF6 , have been carried out in the X-band region. A temperature dependent study of the zero-field splitting parameter D in the range 77-398 K shows the presence of a phase transition, which is supported by Differential Thermal Analysis. In addition, 19F superhyperfine struc-ture has been observed in the 9.3% naturally abundant 53Cr isotope hyperfine structure. D shows a large decrease with increasing temperature. The phase transition brings about a chemical inequivalence in the two chemically equivalent but magnetically inequivalent room temperature (CrF6)3- species. Compar-ison is made with the alums AlCl3 • 6H20, as well as other guanidinium aluminum salts.

An Electron Paramagnetic Resonance Study of Mn2+ Ions Doped in Langbeinites

1992 ◽  
Vol 47 (7-8) ◽  
pp. 849-856 ◽  
Author(s):  
T. Böttjer ◽  
G. Lehmann ◽  
M. Stockhausen
Keyword(s):  
Electron Paramagnetic Resonance Study ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Paramagnetic Resonance ◽  
Zero Field Splitting Parameter ◽  
Splitting Parameter ◽  
Local Relaxation ◽  
Cation Size

Abstract The cubic (high temperature) phase of some langbeinites, A+2 B22+(SO4)3 with 11 different combinations of A and B type cations, doped with Mn2+, is investigated by EPR. Powder or single crystal spectra are measured at X-band. They indicate centers of axial symmetry in all cases. In 6 of the langbeinites two centers are found which differ considerably in intensity. Both centers are substitutional defects (Mn in the crystallographically nonequivalent divalent B ion sites). For the more intense one the zero field splitting parameter is proved to be negative in all cases. That center is assigned to the more spacious site which, depending on the cation size, allows for local relaxation. It is shown by comparison with predictions of the superposition model that relaxation appears to be effective

Correlation of Zero Field Splittings and Site Distortions III. MnBr42- and Crystal Structure Refinements for Rb3ZnBr5 and Cs2ZnBr4

1981 ◽  
Vol 36 (3) ◽  
pp. 286-293 ◽  
Author(s):  
M. Heming ◽  
G. Lehmann ◽  
G. Henkel ◽  
B. Krebs
Keyword(s):  
Fine Structure ◽  
Single Crystals ◽  
Zero Field ◽  
Positive Contribution ◽  
Zero Field Splitting ◽  
Zero Field Splitting Parameter ◽  
Hyperfine Splitting Constant ◽  
Splitting Parameter ◽  
Splitting Constant ◽  
First Time

EPR data for Mn2+ in Cs2ZnBr4, Rb3ZnBr5, Cs3CdBr5 and [(CH3)4N]2ZnBr4 single crystals were determined and the crystal structures of Rb3ZnBr5 and Cs2ZnBr4 were refined. Superposition analysis of the fine structure data for the latter two compounds resulted in an intrinsic zero field splitting parameter b̄2 for MnBr42- of + 0.44 cm-1 suggesting a sizeable positive contribution of covalency. Cs3CdBr5 was prepared in single crystals for the first time. It crystallizes in a primitive tetragonal space group. From the fine structure parameter 62° and the above value of b̄2 an elongation of the CdBr42- tetrahedra along the c-axis with a bond angle of 105.7° was determined. This result is in agreement with the anisotropy of the 55Mn hyperfine splitting constant with A|| = -68.6 and A±= - 70.6 • 10-4 cm-1

Crystal Structure of and Electron Paramagnetic Resonance of Mn2+ in Cd2(NH4)2(SO4)3

1975 ◽  
Vol 53 (10) ◽  
pp. 1449-1455 ◽  
Author(s):  
Hok Nam Ng ◽  
Crispin Calvo
Keyword(s):  
Group Symmetry ◽  
Temperature Structure ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Paramagnetic Resonance ◽  
Space Group ◽  
Zero Field Splitting Parameter ◽  
Charge Model ◽  
Splitting Parameter ◽  
Experimental Values

The room temperature structure of Cd2(NH4)2(SO4)3 (CAS), isotypic with the mineral langbeinite K2Mg2(SO4)3 has been refined by full-matrix least squares methods. The structure is cubic with a = 10.362(7) Å and space group P213. There are two inequivalent sites for the cation Cd2+ and e.p.r. spectra of doped Mn2+ show that Cd2+ was substituted in both sites with preferential occupancy by Mn2+ in a 1:3 ratio. Refinement of X-ray data on a mixed crystal of the stoichiometry Cd0.84Mn1.16(NH4)2(SO4)3 shows that site I contains 82% Mn2+ while site II has 38%. The zero-field splitting parameter D was calculated for Mn2+ in two sites using a point-charge model and confirms that Mn2+ substitutes into site I with greater preference. Although a monoclinic ferroelectric phase of CAS has been suggested below 90 K, no change in space group symmetry could be detected at 80 K. The proton second moment, calculated by the van Vleck's formula, and compared with the experimental values, suggests a tunneling motion of the protons among the four vertices of the ammonium tetrahedron.

Magnetic Resonances of 51V, 209Bi, Mn2+, and Fe3+in BiVO4Single Crystals

1996 ◽  
Vol 51 (5-6) ◽  
pp. 591-602 ◽  
Author(s):  
Sung Ho Choh
Keyword(s):  
Zero Field ◽  
Zero Field Splitting ◽  
Paramagnetic Resonance ◽  
Principal Axes ◽  
Quadrupole Parameters ◽  
Nuclear Quadrupole ◽  
Magnetic Resonances ◽  
First Time ◽  
Electron Paramagnetic ◽  
Second Order Phase Transition

Abstract Nuclear magnetic resonance (NMR) of 51V and 209Bi, and electron paramagnetic resonance (EPR) of Mn2+ and Fe3+ impurities in ferroelastic BiVO4 single crystals are reviewed. The nuclear quadrupole parameters and principal axes of the two host nuclei, 51V and 209Bi, and the second-or-der zero field splitting tensor of the isoelectronic 3 d5 ions, Mn2+ and Fe3+ , in BiVO4 are determined for the first time. Temperature dependence studies on 51V NMR and Mn2+ EPR confirmed that this crystal undergoes a second order phase transition. The substitutional sites of Mn2+ and Fe3+ in BiVO4 are Bi3+ and V5+, respectively.

Electron Paramagnetic Resonance of Cr4+ in Yx2SiO5

1999 ◽  
Vol 560 ◽  
Author(s):  
Rakhim R. Rakhimov ◽  
Holli D. Horton ◽  
George B. Loutts
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Dipole Interaction ◽  
Orientation Dependence ◽  
Zero Field ◽  
Electron Configuration ◽  
Zero Field Splitting ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Rhombic Symmetry ◽  
Electron Paramagnetic

ABSTRACTChromium-doped yttrium orthosilicate Cr:Y2SiO5 was studied by electron paramagnetic resonance (EPR) method at 9.5–9.7 GHz. EPR transitions were observed for Cr4+ substituting Si4+ in tetrahedral sites of Y2SiO5, and orientation dependence of the single crystal EPR spectrum was studied. The ground state of Cr4+ (electron configuration 3d2) in Y2SiO5 is a spin triplet (S = 1). Rhombic symmetry of the electron magnetic dipole-dipole interaction (zero field splitting) leads to three electron spin terms Tx, Ty and Tz in the absence of the external magnetic field. We have observed the magnetically induced anti-crossing of the terms Ty and Tz.We show that in the vicinity of energy level anti-crossing the linewidths and positions of the resonance lines depend on temperature.

Modulation of the coordination environment: a convenient approach to tailor magnetic anisotropy in seven coordinate Co(ii) complexes

2016 ◽  
Vol 52 (4) ◽  
pp. 753-756 ◽  
Author(s):  
Mamon Dey ◽  
Snigdha Dutta ◽  
Bipul Sarma ◽  
Ramesh Ch. Deka ◽  
Nayanmoni Gogoi
Keyword(s):  
Magnetic Anisotropy ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Field Splitting ◽  
Coordination Environment ◽  
Zero Field Splitting Parameter ◽  
Convenient Approach ◽  
Splitting Parameter ◽  
Remarkable Deviation

Subtle modulation of the coordination environment in seven coordinate Co(ii) complexes leads to a remarkable deviation in the axial zero field splitting parameter (D) in a predictable fashion.

Correlation of Zero Field Splittings and Site Distortions V. Mn2+ in Cs2Zn3S4

1983 ◽  
Vol 38 (2) ◽  
pp. 149-153 ◽  
Author(s):  
M. Heming ◽  
G. Lehmann
Keyword(s):  
Fine Structure ◽  
Hyperfine Splitting ◽  
Site Symmetry ◽  
Zero Field ◽  
Structure Parameters ◽  
Zero Field Splitting ◽  
Zero Field Splitting Parameter ◽  
Free Ion ◽  
Splitting Parameter ◽  
Epr Signal

Abstract In platelets of Cs2Zn3S4 with about 4% of the Zn substituted by Mn two nonequivalent centers of isolated Mn2+ were observed in addition to a broad EPR signal near g = 2 which is assigned to clusters of interconnected MnS4 units. The fine structure and hyperfine structure parameters for the single-ion centers (all in units of 1CT 4 cm -1) areb02 = -318.3 ± 3; b22 = -210.3 ± 2; Ay = -62.7; Az = -63.6 ± 0.8;b02 = -890 ± 18; b22 = -743 ± 36; Ay = -60.6; Az = - 61.4 ± 0.8;for centers I and II, resp. Center II arises from Zn sites of C 2 site symmetry while for center I assignment to either one of two sites with D2 site symmetry is possible. The larger hyperfine splitting constants as well as the superposition analysis favor the larger sites which are not occupied by Zn, but are partly occupied in the analogous Mn (and Co) compounds. Superposition analysis yields the same value of + 0.12 ± 0.02 cm-1 for the intrinsic zero field splitting parameter b̄2 of the bridging MnS4 units in both sites. gz is significantly higher than the free ion value indicating a higher degree of covalency than in Cds and CdGa2S4.

scholarly journals Concentration of Fe(3+)-Triapine in BEAS-2B Cells

2019 ◽  
Vol 20 (12) ◽  
pp. 3062 ◽  
Author(s):  
William E. Antholine ◽  
Charles R. Myers
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Tumor Cells ◽  
Iron Uptake ◽  
Antitumor Agent ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Epr Method ◽  
First Time ◽  
Electron Paramagnetic ◽  
In Cells

An electron paramagnetic resonance (EPR) method was used to determine the concentration of the antitumor agent Triapine in BEAS-2B cells when Triapine was bound to iron (Fe). Knowledge of the concentration of Fe-Triapine in tumor cells may be useful to adjust the administration of the drug or to adjust iron uptake in tumor cells. An EPR spectrum is obtained for Fe(3+)-Triapine, Fe(3+)(Tp)2+, in BEAS-2B cells after addition of Fe(3+)(Tp)2+. Detection of the low spin signal for Fe(3+)(Tp)2+ shows that the Fe(3+)(Tp)2+ complex is intact in these cells. It is proposed that Triapine acquires iron from transferrin in cells including tumor cells. Here, it is shown that iron from purified Fe-transferrin is transferred to Triapine after the addition of ascorbate. To our knowledge, this is the first time that the EPR method has been used to determine the concentration of an iron antitumor agent in cells.

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