scholarly journals High temperature EPR study of the M3Fe4V6O24 (M = Cu, Zn, Mg and Mn)

2016 ◽  
Vol 34 (3) ◽  
pp. 517-522 ◽  
Author(s):  
Niko Guskos ◽  
Grzegorz Zolnierkiewicz ◽  
Janusz Typek ◽  
Malwina Pilarska ◽  
Constantinos Aidinis ◽  
...  
Keyword(s):  
High Temperature ◽  
Resonance Field ◽  
Spin Systems ◽  
Magnetic Interactions ◽  
Paramagnetic Resonance ◽  
Integrated Intensity ◽  
Epr Parameters ◽  
Magnetic Ions ◽  
Electron Paramagnetic

AbstractElectron paramagnetic resonance (EPR) spectra of M3Fe4V6O24 (M = Cu, Zn, Mg and Mn) compounds in high temperature range (293 K to 493 K) have been investigated. The role of magnetic (Cu, Mn) and non-magnetic (Zn, Mg) ions in M3Fe4V6O24 structure in formation of magnetic resonance spectra was studied. Temperature dependence of EPR parameters: resonance field, linewidth and integrated intensity were examined. Similarities and differences in temperature behavior of these parameters has been discussed in terms of different relaxation mechanisms and magnetic interactions in the spin systems. An important role of additional magnetic ions (M = Mn or Cu) in the M3Fe4V6O24 structure has been identified and its consequences considered.

Spectroscopic and Magnetic Properties of Gadolinium Macroacyclic and Macrobicyclic Complexes

2007 ◽  
Vol 128 ◽  
pp. 199-205
Author(s):  
G. Leniec ◽  
Slawomir M. Kaczmarek ◽  
J. Typek ◽  
Beata Kołodziej ◽  
Eugeniusz Grech ◽  
...  
Keyword(s):  
Schiff Base ◽  
Metal Ion ◽  
Molecular Spectroscopy ◽  
Schiff Base Complex ◽  
Schiff Base Complexes ◽  
Magnetic Interactions ◽  
Paramagnetic Resonance ◽  
Complex Samples ◽  
Integrated Intensity ◽  
Electron Paramagnetic

As a result of the Schiff base condensation the gadolinium macroacyclic and macrobicyclic Schiff base complexes have been synthesized and investigated by infrared spectroscopy (IR) and electron paramagnetic resonance (EPR). Both electron ionization and electron spray Molecular Spectroscopy spectra confirmed the [1:1] proportion of a ligand to metal in gadolinium macrocyclic and mocrobicyclic Schiff base complex samples. The thermogravimetrydifferential thermal analysis (TG-DTA) indicated the presence of two water molecules in the innersphere of the macrobicyclic complex and confirmed no water coordination of the metal ion in the macroacyclic complex. The temperature dependence of the integrated intensity of the EPR spectra enabled the magnetic interactions in the spin system of these compounds to be revealed.

scholarly journals EPR Spectra of Sintered Cd1−xCrxTe Powdered Crystals with Various Cr Content

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3449
Author(s):  
Ireneusz Stefaniuk ◽  
Werner Obermayr ◽  
Volodymyr D. Popovych ◽  
Bogumił Cieniek ◽  
Iwona Rogalska
Keyword(s):  
Curie Temperature ◽  
Room Temperature ◽  
Integral Intensity ◽  
Resonance Field ◽  
Epr Spectra ◽  
Paramagnetic Resonance ◽  
Simple Method ◽  
Paramagnetic Curie Temperature ◽  
Cr Content ◽  
Electron Paramagnetic

In this paper, we show a simple method of producing ferromagnetic materials with a Curie temperature above room temperature. The electron paramagnetic resonance (EPR) spectra of Cd1−xCrxTe (0.002 < x < 0.08) were measured with a dependence on temperature (82 K < T < 381 K). Obtained EPR lines were fitted to a Lorentz-shaped curve. The temperature dependencies of the parameters of the EPR lines, such as the peak-to-peak linewidth (Hpp), the intensity (A), as well as the resonance field (Hr), were studied. Ferromagnetism was noticed in samples at high temperatures (near room temperature). For a sample with a nominal concentration of chrome of x = 0.05, a very strong intrinsic magnetic field is observed. The value of the effective gyromagnetic factor for this sample is ge = 30 at T = 240 K. An increase of chrome concentration above x = 0.05 reduces the ferromagnetic properties considerably. Analysis of the temperature dependencies of the integral intensity of EPR spectra was carried out using the Curie–Weiss law and the paramagnetic Curie temperature was obtained.

The Microscopic Structure Of Shallow Donors In Silicon Carbide

1996 ◽  
Vol 442 ◽  
Author(s):  
J.-M. Spaeth ◽  
S. Greulich-Weber ◽  
M. März ◽  
E. N. Kalabukhova ◽  
S. N. Lukin
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Double Resonance ◽  
Epr Spectra ◽  
Electron Nuclear Double Resonance ◽  
Paramagnetic Resonance ◽  
Vacancy Pair ◽  
Temperature Spectra ◽  
Electron Paramagnetic

AbstractThe electronic structure of nitrogen donors in 6H-, 4H- and 3C-SiC is investigated by measuring the nitrogen hyperfine (hf) interactions with electron nuclear double resonance (ENDOR) and the temperature dependence of the hf split electron paramagnetic resonance (EPR) spectra. Superhyperfine (shf) interactions with many shells of 13C and 29Si were measured in 6H-SiC. The hf and shf interactions are discussed in the framework of effective mass theory. The temperature dependence is explained with the thermal occupation of the lowest valley-orbit split A1 and E states. It is proposed that the EPR spectra of P donors observed previously in neutron transmuted 6H-SiC at low temperature (<10K) and high temperature (>60K) are all due to substitutional P donors on the two quasi-cubic and hexagonal Si sites, whereby at low temperature the E state is occupied and at high temperature the A1 state. The low temperature spectra are thus thought not to be due to P-vacancy pair defects as proposed previously.

Studies of local structures for Cu2+ centers in M2Zn(SO4)2·6H2O (M = NH4 and Rb) crystals

2021 ◽  
Vol 76 (4) ◽  
pp. 299-304
Author(s):  
Fu Chen ◽  
Jian-Rong Yang ◽  
Zi-Fa Zhou
Keyword(s):  
Crystal Field ◽  
Elongation Ratio ◽  
Paramagnetic Resonance ◽  
Local Structures ◽  
Epr Parameters ◽  
Structure Constants ◽  
Crystal Field Parameters ◽  
Electron Paramagnetic ◽  
Theoretical Results ◽  
Good Agreement

Abstract The electron paramagnetic resonance (EPR) parameters (g factor g i , and hyperfine structure constants A i , with i = x, y, z) and local structures for Cu2+ centers in M2Zn(SO4)2·6H2O (M = NH4 and Rb) are theoretically investigated using the high order perturbation formulas of these EPR parameters for a 3d 9 ion under orthorhombically elongated octahedra. In the calculations, contribution to these EPR parameters due to the admixture of d-orbitals in the ground state wave function of the Cu2+ ion are taken into account based on the cluster approach, and the required crystal-field parameters are estimated from the superposition model which enables correlation of the crystal-field parameters and hence the studied EPR parameters with the local structures of the Cu2+ centers. Based on the calculations, the Cu–H2O bonds are found to suffer the axial elongation ratio δ of about 3 and 2.9% along the z-axis, meanwhile, the planar bond lengths may experience variation ratio τ (≈3.8 and 1%) along x- and y-axis for Cu2+ center in (NH4)2Zn(SO4)2·6H2O and Rb2Zn(SO4)2·6H2O, respectively. The theoretical results show good agreement with the observed values.

INVESTIGATIONS OF ELECTRON-PARAMAGNETIC-RESONANCE PARAMETERS OF OCTAHEDRAL (CrO6)9- and (MnO6)8- CLUSTER IN MgTiO3:Cr3+, SrTiO3:Cr3+ AND SrTiO3:Mn4+ CRYSTALS

2011 ◽  
Vol 25 (21) ◽  
pp. 1779-1785
Author(s):  
MINJIE WANG ◽  
LIANXUAN ZHU ◽  
JIANLIANG DANG
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Crystal Field ◽  
Valence State ◽  
Spin Orbit ◽  
Contribution Rate ◽  
Paramagnetic Resonance ◽  
Epr Parameters ◽  
Experimental Values ◽  
Electron Paramagnetic ◽  
G Factors

The complete high-order perturbation formulas are established by both crystal-field (CF) and charge-transfer (CT) mechanisms. The EPR g factors of MgTiO 3: Cr 3+, SrTiO 3: Cr 3+ and SrTiO 3: Mn 4+ crystals are calculated from the formulas. The calculations of the EPR g factors are in agreement with the experimental values. The contribution rate of the CT mechanism (|ΔgT/ΔgF|) to EPR parameters, increases with the growth of the valence state for the 3dn ions in the crystals. For the higher valence state 3d3 ion Mn 4+ in crystals, the explanation of the EPR parameters reasonably involves both CF and CT mechanisms. The g values are also given from one-spin-orbit-parameter model and crystal-field (CF) mechanism for comparison.

EPR INVESTIGATIONS OF CuO-B2O3-PbO-Ag2O GLASSES

2009 ◽  
Vol 23 (05) ◽  
pp. 747-753
Author(s):  
VIOREL TIMAR ◽  
RALUCA CICEO-LUCÃCEL ◽  
OCTAVIA HULPUŞ ◽  
IOAN ARDELEAN
Keyword(s):  
Copper Content ◽  
Structural Modification ◽  
Magnetic Interactions ◽  
Paramagnetic Resonance ◽  
Distorted Octahedral ◽  
Structural Details ◽  
Paramagnetic Probes ◽  
Parallel Band ◽  
Electron Paramagnetic ◽  
Epr Experiments

Glasses of the x CuO · (100 - x)[3 B 2 O 3· 0.9 PbO · 0.1 Ag 2 O ] system, with 0.5 ≤ x ≤ 10 mol %, were prepared and investigated by means of electron paramagnetic resonance (EPR) measurements. Structural details of different diamagnetic vitreous systems may be revealed by the Cu 2+ ions, frequently used as paramagnetic probes in EPR experiments. The shape and the intensity of the recorded EPR lines are dependent on the CuO content. The EPR spectra are asymmetric, with characteristics for Cu 2+ (3d9) ions in axially-distorted octahedral symmetric sites. Due to the interaction of the unpaired electron spin (s = 1/2) with the nuclear one (I = 3/2) of Cu 2+ ions, the characteristic hyperfine structure (hfs) is visible for small concentrations of CuO in both spectra bands (parallel and perpendicular). The increasing of copper content in the samples generates the EPR absorption spectra modification, the hfs being resolved in the parallel band of the spectra in whole compositional range, while in the perpendicular band, hfs disappear for x > 3 mol %. This fact indicates the structural modification in Cu 2+ vicinity and possible magnetic interactions.

scholarly journals DFT Protocol for EPR Prediction of Paramagnetic Cu(II) Complexes and Application to Protein Binding Sites

2018 ◽  
Vol 4 (4) ◽  
pp. 55 ◽  
Author(s):  
Giuseppe Sciortino ◽  
Giuseppe Lubinu ◽  
Jean-Didier Maréchal ◽  
Eugenio Garribba
Keyword(s):  
Binding Sites ◽  
Density Functional ◽  
Computational Procedure ◽  
Paramagnetic Resonance ◽  
Functional Theory ◽  
Protein Binding Sites ◽  
The Mean ◽  
Hamiltonian Parameters ◽  
Electron Paramagnetic

With the aim to provide a general protocol to interpret electron paramagnetic resonance (EPR) spectra of paramagnetic copper(II) coordination compounds, density functional theory (DFT) calculations of spin Hamiltonian parameters g and A for fourteen Cu(II) complexes with different charges, donor sets, and geometry were carried out using ORCA software. The performance of eleven functionals was tested, and on the basis of the mean absolute percent deviation (MAPD) and standard deviation (SD), the ranking of the functionals for Az is: B3LYP > B3PW91 ~ B3P86 > PBE0 > CAM-B3LYP > TPSSh > BH and HLYP > B2PLYP > MPW1PW91 > ω-B97x-D >> M06; and for gz is: PBE0 > BH and HLYP > B2PLYP > ω-B97x-D > B3PW91~B3LYP~B3P86 > CAM-B3LYP > TPSSh~MPW1PW91 >> M06. With B3LYP the MAPD with respect to A z exp t l is 8.6% with a SD of 4.2%, while with PBE0 the MAPD with respect to g z exp t l is 2.9% with a SD of 1.1%. The results of the validation confirm the fundamental role of the second order spin-orbit contribution to Az. The computational procedure was applied to predict the values of gz and Az of the adducts formed by Cu(II) with albumin and two fragments of prion protein, 106–126 and 180–193.

scholarly journals PQQ-Aza-Crown Ether Complexes as Biomimetics for Lanthanide and Calcium Dependent Alcohol Dehydrogenases

2021 ◽  
Author(s):  
Violeta A. Vetsova ◽  
Katherine R. Fisher ◽  
Henning Lumpe ◽  
Alexander Schäfer ◽  
Erik K. Schneider ◽  
...  
Keyword(s):  
Metal Ions ◽  
Gas Phase ◽  
Ion Mobility ◽  
Paramagnetic Resonance ◽  
Calcium Dependent ◽  
Lower Charge ◽  
Crown Ether Complexes ◽  
Recent Group ◽  
Electron Paramagnetic

<div>Understanding the role of metal ions in biology can lead to the development of new catalysts for</div><div>several industrially important transformations. Lanthanides are the most recent group of metal ions</div><div>that have been shown to be important in biology i.e. - in quinone-dependent methanol</div><div>dehydrogenases (MDH). Here we evaluate a pyrroloquinoline quinone and 1-aza-15-crown-5 based</div><div>ligand platform as scaffold for Ca2+ , Ba2+ , La3+ and Lu3+ biomimetics of MDH and we evaluate the</div><div>importance of ligand design, charge, size, counterions and base for the alcohol oxidation reaction</div><div>using NMR spectroscopy. In addition, we report a new straightforward synthetic route (3 steps</div><div>instead of 11 and 33% instead of 0.6% yield) for biomimetic ligands based on PQQ. We show that</div><div>when studying biomimetics for MDH, larger metal ions and those with lower charge in this case</div><div>promote the dehydrogenation reaction more effectively and that this is likely an effect of the ligand</div><div>design which must be considered when studying biomimetics. To gain more information on the</div><div>structures and impact of counterions of the complexes, we performed collision induced dissociation</div><div>(CID) experiments and observe that the nitrates are more tightly bound than the triflates. To resolve</div><div>the structure of the complexes in the gas phase we combined DFT-calculations and ion mobility</div><div>measurements (IMS). Furthermore, we characterized the obtained complexes and reaction mixtures</div><div>using Electron Paramagnetic Resonance (EPR) spectroscopy and show the emergence of a quinone-</div><div>based radical during the reaction with substrate and base.</div>

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