The spin-Hamiltonian parameter temperature dependence of the EPR spectra of Gd3+ impurity ions in Y(OH)3 and Eu(OH)3

1984 ◽  
Vol 62 (2) ◽  
pp. 126-133 ◽  
Author(s):  
H. A. Buckmaster ◽  
V. M. Malhotra ◽  
J. M. Boteler
Keyword(s):  
Temperature Variation ◽  
Ion Pairs ◽  
Spin Hamiltonian Parameter ◽  
Linear Functions ◽  
Zero Field ◽  
Spin Hamiltonian ◽  
Zero Field Splitting ◽  
Measurement Interval ◽  
Crystalline Electric Field ◽  
Impurity Ions

The 9.23 GHz electron paramagnetic resonance (EPR) spectrum of ~1% Gd3+ impurity ions in Y(OH)3 and Eu(OH)3 monocrystals has been measured from 11 to 296 K. These spectra have been analyzed using a C3h symmetry, phenomenological spin-Hamiltonian. The temperature variation of the spin-Hamiltonian parameters was fitted to empirical root-mean-square (rms) best-fit expressions. It was found that the g values are linear functions of the temperature and that the nearest neighbour (nn) exchange interaction, Jnn = +0.23(5) cm−1 for (Gd3+−Eu3+) ion pairs, can be estimated from the single ion data. This is in satisfactory agreement with Jnn = +0.06(9) cm−1 obtained from ion pair data. The temperature variation of the zero field splitting (ZFS) parameters B20 and B40was found to fit cubic expressions over the temperature measurement interval and the magnitude of B20 increased as the temperature increased, corroborating the earlier conclusion that the host lattice effect in the Ln(OH)3 series cannot be explained using a point charge model for the crystalline electric field.

EPR Study of the Nitrogen Containing Defect Center Created in Self-Assembled 6H SiC Nanostructure

2013 ◽  
Vol 740-742 ◽  
pp. 389-392 ◽  
Author(s):  
Ekaterina N. Kalabukhova ◽  
Dariya Savchenko ◽  
Bela Shanina ◽  
Nikolai T. Bagraev ◽  
Leonid Klyachkin ◽  
...  
Keyword(s):  
The Self ◽  
Zero Field ◽  
Boron Diffusion ◽  
Spin Hamiltonian ◽  
Zero Field Splitting ◽  
Epr Spectrum ◽  
Defect Center ◽  
Field Splitting ◽  
Splitting Constant ◽  
Self Assembled

Triplet center with spin state S = 1 is detected in the EPR spectrum of the self-assembled 6H SiC nanostructure obtained by non-equilibrium boron diffusion into the n-type 6H SiC epitaxial layer (EL) under conditions of the controlled injection of the silicon vacancies at the temperature of T = 900°C. From the analysis of the angular dependences of the EPR spectrum and the numerical diagonalization of the spin Hamiltonian, the value of the zero-field splitting constant D and g-factor are found to be D = 1140•10-4см-1 and gpar = 1.9700, gper = 1.9964. Based on the hyperfine (hf) structure of the defect originating from the hf interaction with one 14N nuclei, the large value of the zero-field splitting constant D and technological conditions of the boron diffusion into the n-type 6H SiC EL, the triplet center is tentatively assigned to the defect center consisting of nitrogen atom and silicon vacancy.

scholarly journals EPR of Compound I: An Illustrated Revision of the Theoretical Model

2020 ◽  
Vol 51 (11) ◽  
pp. 1559-1589
Author(s):  
Maruan Bracci ◽  
Sabine Van Doorslaer ◽  
Inés García-Rubio
Keyword(s):  
Free Radical ◽  
Energy Levels ◽  
Magnetic Interaction ◽  
Local Environment ◽  
Paramagnetic Species ◽  
Zero Field ◽  
Spin Hamiltonian ◽  
Compound I ◽  
Zero Field Splitting ◽  
Counter Rotation

AbstractCompound I has been postulated to be the reactive species in many heme catalysts, which performs different chemistry and shows different properties in different enzymes. The aim of this review is to present a comprehensive model which has been successfully used to interpret the EPR spectra of various Compound I species. The theoretical approach established by seminal articles will be revisited and its ability to explain experimental results will be illustrated by simulating selected spectra from the literature. Compound I stores two oxidizing equivalents, one in the paramagnetic iron(IV)-oxo moiety, and another one as a free radical on the porphyrin ligand or an amino acid in the protein. To describe the interactions of the two paramagnetic species with each other and with their local environment, the spin Hamiltonian of the system is built step by step. The Fe(IV) center is described using a two-hole model. The effect of the crystal-field and spin–orbit coupling on the energy levels is calculated with this simple approach, which allows to obtain spin Hamiltonian parameters like zero-field splitting and effective g-values for the iron. The magnetic interaction between the Fe(IV) center and the free radical is considered and allowed to vary in sign (ferromagnetic to antiferromagnetic) and magnitude to interpret the EPR of Compound I species in different systems. Since orbital overlap is crucial for exchange interaction, special emphasis is made in obtaining the orientation of Fe semi-occupied orbitals by extending the counter-rotation concept, which relates the directions of magnetic, electronic, and molecular axes.

ESR SPECTRA OF Fe+3 IN SINGLE CRYSTALS OF ANDALUSITE

1966 ◽  
Vol 44 (3) ◽  
pp. 509-523 ◽  
Author(s):  
F. Holuj ◽  
J. R. Thyer ◽  
N. E. Hedgecock
Keyword(s):  
Single Crystals ◽  
Room Temperature ◽  
Esr Spectra ◽  
Zero Field ◽  
Spin Hamiltonian ◽  
Zero Field Splitting ◽  
Field Splitting ◽  
K Band

ESR spectra of Fe+3 in andalusite have been investigated at X- and K-band frequencies at room temperature. They have been interpreted on the assumption that Fe+3 occupies the two inequivalent Al+3 sites in andalusite. The spectra show large zero-field splitting. The constants of the conventional orthorhombic spin Hamiltonian which fit the spectra are as follows: for site I: b20 = 15.0 ± 0.1 kG, b22 = 5.0 ± 0.1 kG, and isotropic g = 2.001 ± 0.002; for site II: b20 = 20.1 ± 0.1 kG, b22 = 0.075 ± 0.010 kG, and isotropic g = 2.004 ± 0.0005. A study of the intensities of ESR signals due to site I follow a pattern predicted by theory. The implications of these results are considered briefly.

ELECTRON SPIN RESONANCE OF Fe+3 IN CORDIERITE

1966 ◽  
Vol 44 (11) ◽  
pp. 2749-2755 ◽  
Author(s):  
N. E. Hedgecock ◽  
S. C. Chakravartty
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Room Temperature ◽  
Esr Spectra ◽  
Orthorhombic Symmetry ◽  
Zero Field ◽  
Spin Hamiltonian ◽  
Zero Field Splitting ◽  
Field Splitting ◽  
Spin Resonance

ESR spectra of Fe+3 located at one of the aluminium sites in cordierite have been investigated at X- and K-band frequencies at room temperature. The spectra exhibit large zero-field splitting and have been fitted to a spin Hamiltonian of orthorhombic symmetry, having constants b20 = 14.6 ± 0.1 kG, b22 = 8.5 ± 0.1 kG, and isotropic g = 2.004 ± 0.002.

A study of the host lattice effect in the lanthanide hydroxides. 34 GHz Gd3+ impurity ion EPR spectra at 77 and 294 K

1982 ◽  
Vol 60 (11) ◽  
pp. 1573-1588 ◽  
Author(s):  
V. M. Malhotra ◽  
H. A. Buckmaster
Keyword(s):  
Point Charge ◽  
Ionic Radius ◽  
Host Lattice ◽  
Epr Spectra ◽  
Zero Field ◽  
Nearest Neighbour ◽  
Zero Field Splitting ◽  
Impurity Ions ◽  
Lattice Effect ◽  
Impurity Ion

The 34 GHz EPR spectra of 5-state (4f7, 8S) Gd3+ impurity ions (~1%) in the isostructural [Formula: see text] symmetry Ln(OH)3 host lattice (Ln ≡ La, Sm, Eu, Tb, Ho, Y) have been studied at 77 and 294 K. The expected seven line ΔM = ± 1 spectrum is observed for Ln = La, Eu, Ho, and Y whereas only a single broad transition is observed for Ln ≡ Sm and Tb. The observed values of the zero field splitting (ZFS) parameter B20 as well as the TZFS are found to be related linearly to (i) the ionic radius, (ii) the Ln–O1 distance, and (iii) the Ln–O2 distance where O1 and O2 are the nearest neighbour equatorial and apical oxygens. However, the slopes are opposite to that predicted by a point charge lattice model. This paper discusses (i) the SH parameters, (ii) the host lattice effect, (iii) the ZFS processes, and (iv) the linewidths observed in the Ln(OH)3 host lattice and attempts to explain the observations using the existing theory. It is found that this apparently simple host lattice exhibits complex effects which do not change systematically with the host lanthanide ion, unlike that observed in most other isostructural lanthanide hosts that have been studied using Gd3+ impurity ions.

INVESTIGATION OF THE DEFECT STRUCTURE, OPTICAL AND EPR SPECTRA FOR CdS: Ti2+ AND CdSe: Ti2+ CRYSTAL

2009 ◽  
Vol 23 (27) ◽  
pp. 5325-5331 ◽  
Author(s):  
WEN-LIN FENG ◽  
WEN-CHEN ZHENG
Keyword(s):  
Defect Structure ◽  
Spectral Band ◽  
Zero Field ◽  
Spin Orbit ◽  
Defect Structures ◽  
Spin Hamiltonian ◽  
Zero Field Splitting ◽  
Orbit Parameter ◽  
Crystal Field Parameters ◽  
Hamiltonian Parameters

The optical spectral band positions and spin-Hamiltonian parameters (g factors g‖, g⊥ and zero-field splitting D) of CdS : Ti 2+ and CdSe : Ti 2+ crystals are calculated from the complete diagonalizaion (of energy matrix) method based on a two-spin-orbit parameter model for 3d2 ions in trigonal symmetry. In the model, both the contribution to spin-Hamiltonian parameters due to the spin-orbit parameter of central 3d2 ions and that of ligand ions are included. The crystal field parameters used in the calculations are obtained from the superposition model which enables correlation of the optical and EPR spectral data with the defect structure of the studied paramagnetic impurity centers in crystals. From the calculations, the defect structures of Ti 2+ centers in CdS : Ti 2+ and CdSe : Ti 2+ are acquired, the signs of zero-field splittings D are suggested, and the optical band positions and spin-Hamiltonian parameters are explained. The results are discussed.

Studies of the Spin Hamiltonian Parameters for NiX2 and CdX2:Ni2+ (X=Cl, Br)

2009 ◽  
Vol 282 ◽  
pp. 25-30
Author(s):  
Zhi Hong Zhang ◽  
Shao Yi Wu ◽  
Xue Feng Wang ◽  
Yue Xia Hu
Keyword(s):  
Zero Field ◽  
Spin Hamiltonian ◽  
Zero Field Splitting ◽  
Local Structures ◽  
Ligand Orbital ◽  
Distorted Octahedra ◽  
Lattice Distortions ◽  
Hamiltonian Parameters ◽  
Ligand Bond ◽  
G Factors

The spin Hamiltonian parameters (zero-field splitting D and the g factors) for NiX2 and CdX2:Ni2+ (X=Cl, Br) are quantitatively investigated from the perturbation formulas of these parameters for a 3d8 ion in trigonally distorted octahedra based on the cluster approach. In the calculations, the trigonal field parameters  and ′ are determined from the superposition model and the local structures of Ni2+ in the halides. The theoretical g factors show reasonable agreement with the observed values, and the experimental D for CdX2:Ni2+ are also interpreted by considering suitable lattice distortions (angular decreases) in the impurity-ligand bond angles related to the C3 axis due to the size mismatching substitution. The contributions from the ligand orbital and spin-orbit coupling interactions are important and should be taken into account.

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