The magnetic properties of the oxygen–hole aluminum centers in crystalline SiO2. II. [AlO4/H+]+ and [AlO4/Li+]+

1981 ◽  
Vol 59 (11) ◽  
pp. 1709-1718 ◽  
Author(s):  
R. H. D. Nuttall ◽  
J. A. Weil
Keyword(s):  
Magnetic Properties ◽  
Spin Hamiltonian Parameter ◽  
Spin Hamiltonian ◽  
Hole Trapping ◽  
Hamiltonian Parameter ◽  
Oxygen Hole ◽  
Charge Compensator ◽  
X Irradiation ◽  
Hyperfine Splittings ◽  
A Charge

The centers [AlO4/M+]+, formed in α-quartz by X-irradiation at 77 K, contain an aluminum ion substituted for a silicon ion, with an electron removed from a neighboring oxygen by the ionizing radiation. In addition, there is an interstitial ion M+ which acted as a charge compensator before the irradiation. Centers [AlO4/H+]+ and [AlO4/Li+]+ have been re-examined by EPR (at ca. 35 K), including measurement of small hyperfine splittings due to the compensator ions. The spin-Hamiltonian parameter matrices (i.e., [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]) show that the hole-trapping oxygen in these species is linked via a "short" bond to aluminum (there are two different Si–O bond lengths in quartz). The probable positions of the compensating ions (Li+, H+) in a channel parallel to the crystallographic c-axis are reported.

EPR Analysis of Copper Exchanged and Encapsulated Copper (SALEN) Complex in Zeolite - Y

1994 ◽  
Vol 368 ◽  
Author(s):  
N Ulagappan ◽  
V Krishnasamy
Keyword(s):  
Copper Complex ◽  
Zeolite Y ◽  
Spin Hamiltonian Parameter ◽  
Epr Spectra ◽  
Spin Hamiltonian ◽  
Salen Complex ◽  
Hamiltonian Parameter

ABSTRACTCopper exchanged and copper-(salen) complex encapsulated in zeolite-Y were prepared. The encapsulaled complex was analysed by TGA, DRS and IR, which confirms the presence of complex in zeolite. Both copper materials were examined by EPR spectra, and the calculated spin-Hamiltonian parameter indicates the copper complex is more covalent in character than NaCu-Y.

Paramagnetic Ge–Li centres in alpha quartz revisited: The DLi([GeO4/Li]0D) centre

2008 ◽  
Vol 86 (11) ◽  
pp. 1303-1311
Author(s):  
R F.C. Claridge ◽  
O M Kryliouk ◽  
J A Weil ◽  
J A.S. Williams
Keyword(s):  
Electron Paramagnetic Resonance Spectroscopy ◽  
Spin Hamiltonian Parameter ◽  
Resonance Spectroscopy ◽  
Paramagnetic Defect ◽  
Paramagnetic Resonance ◽  
Hamiltonian Parameter ◽  
X Band ◽  
X Irradiation ◽  
And Storage ◽  
Electron Paramagnetic

A previously unreported stable paramagnetic defect centre in single-crystal alpha-quartz has been studied by quantitative X-band electron paramagnetic resonance spectroscopy at 15, 100, and 296 K, and is shown to contain a Ge3+ ion, presumably located substitutional for Si4+, with a nearby interstitial Li+ ion. The centre, called DLi herein, grows in slowly (months) after room-temperature x-irradiation and storage. Hyperfine structure arising from 73Ge, 7Li, and 29Si has been observed. The spin-Hamiltonian parameter matrices g, A(7Li), A(73Ge), and P(73Ge) are reported, also for centre CLi. A thermal dynamic process, probably involving Li+ hopping, begins to be appreciable above 100 K. Discussion of DLi, its apparent growth from another paramagnetic centre (not yet fully characterized), and comparison with other similar defects is included.PACS Nos.: 42.70.Ce, 61.72.Hh, 61.72–y, 61.72S–, 61.72uf, 61.80–x, 76.30–v, 76.30.Mi

Defect structure and formation of defect complexes in Cu2+-modified metal oxides derived from a spin-Hamiltonian parameter analysis

2009 ◽  
Vol 107 (19) ◽  
pp. 1981-1986 ◽  
Author(s):  
Rüdiger-A. Eichel ◽  
Michael D. Drahus ◽  
Peter Jakes ◽  
Ebru Erünal ◽  
Emre Erdem ◽  
...  
Keyword(s):  
Metal Oxides ◽  
Defect Structure ◽  
Spin Hamiltonian Parameter ◽  
Parameter Analysis ◽  
Spin Hamiltonian ◽  
Defect Complexes ◽  
Hamiltonian Parameter

Synthesis, Structure and Magnetic Properties of Monoclinic Nb12O29

2000 ◽  
Vol 658 ◽  
Author(s):  
J. E. L. Waldron ◽  
M. A. Green
Keyword(s):  
Magnetic Properties ◽  
Magnetic Order ◽  
Bulk Sample ◽  
Charge Ordering ◽  
Rapid Reduction ◽  
One Dimensional ◽  
Range Magnetic Order ◽  
A Charge ◽  
Ordering Transition ◽  
Long Range Magnetic Order

ABSTRACTThe synthesis, structure and magnetic properties of monoclinic Nb12O29 are described. The synthesis of a pure bulk sample is difficult due to the large number of other similar phases. It is achieved by rapid reduction of H-Nb2O5 with Nb metal. The compound is shown to undergo a charge ordering transition at low temperature which provokes long range magnetic order in an intriguing one dimensional arrangement.

Thermally reversible γ-ray-induced redox reaction between substitutional iron and aluminum impurity centers in a silica glass

2001 ◽  
Vol 16 (1) ◽  
pp. 127-131 ◽  
Author(s):  
Radhaballabh Debnath
Keyword(s):  
Silica Glass ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Hole Trapping ◽  
Oxygen Hole ◽  
Before And After ◽  
Impurity Centers ◽  
Spin Resonances ◽  
Electron Paramagnetic ◽  
Hole Centers

The magnetic properties of the substitutional iron and aluminum impurity centers in a sintered Vycor silica glass were studied before and after 1.1–1.3 MeV γ irradiation. Observation of two overlapping spin resonances (g ∼ 4.20–4.28) in the spectra of both the irradiated and preirradiated glasses indicated the existence of two types of tetra coordinated substitutional iron centers of the [FeO4−/Na+]0 type. The intensity of these electron-paramagnetic resonance (EPR) signals decreased upon g irradiation of the glass with concomitant generation of aluminum hole center [AlO4]0, which was manifested by the occurrence of a new six-line EPR signal with g 4 2.009, while thermal annealing of these aluminum oxygen hole centers restores the intensity of the iron centers almost to their preirradiation level. This result suggests that if not the whole, a major fraction of the electrons released in the process of g-ray-induced hole trapping at the Al site are captured by the substitutional iron centers. The electron traps, thus formed, are quite stable and can be deactivated by thermal stimulation.

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