Electron–Nuclear Double Resonance of 53Cr3+ in Aluminum Alums

1974 ◽  
Vol 52 (18) ◽  
pp. 1731-1738 ◽  
Author(s):  
A. Manoogian ◽  
B. Auger
Keyword(s):  
Double Resonance ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Electron Nuclear Double Resonance ◽  
Microwave Frequencies ◽  
Straight Line ◽  
Zero Field Splitting Parameter ◽  
X Band ◽  
Splitting Parameter ◽  
D Values

Electron–nuclear double resonance (ENDOR) studies are reported for the isotope 53Cr3+ enriched to 96% in the aluminum alums RbAl(SO4)2∙12H2O and CsAl(SO4)2∙12H2O. The measurements were made at 4.2 K and X-band microwave frequencies (~9.4 GHz). The values of the spin Hamiltonian hyperfine parameters A, B, and Q′ are found to be quite similar to those obtained previously in the corresponding gallium alums even though the zero field splitting parameter D is significantly different. A plot of A − B vs. Q′ indicates that the amount of distortion existing at a chromium site can be related to the type of monovalent ion present, i.e. Rb or Cs. It is possible to draw straight line curves relating the parameters Q′ vs. D, A − B vs. D, and Vzz vs. D which account quite well for all the ENDOR data obtained so far in the alums and GAISH and which could be generally true for chromium magnetic complexes in crystals with D values not too close to zero.

A Concept to Relate the ZFS Parameter D of Aromatic Hydrocarbons to Molecular and Electronic Structure

1979 ◽  
Vol 34 (2) ◽  
pp. 265-268
Author(s):  
Chr. Bräuchle ◽  
H. Kabza ◽  
J. Voitländer
Keyword(s):  
Aromatic Hydrocarbons ◽  
Dipole Interaction ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Aromatic Molecules ◽  
Zero Field Splitting Parameter ◽  
Pyrene Derivatives ◽  
Splitting Parameter ◽  
D Values ◽  
Molecular And Electronic Structure

Abstract New aspects for the interpretation of the zero field splitting parameter D of the lowest excitet triplet state of polycyclic hydrocarbons are presented. A model connecting the dipole-dipole interaction between the two triplet electrons with Clar’s concept of electronic sextets is employed. It follows that even in highly condensed aromatic molecules the probability for the two triplet electrons to be localized on one C6-ring unit can be relative high.This concept is outlined taking the experimental D-values of a series of pyrene derivatives as an example

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 Abnormal Magnetic Moment and Zero Field Splitting of Some Nickel (II) Complexes

2017 ◽  
Vol 7 (1) ◽  
pp. 34
Author(s):  
Rajeev Ranjan ◽  
Navneet Sinha ◽  
Sahdeo Kumar ◽  
Chandra Mauleshwar Chandra ◽  
Shivadhar Sharma
Keyword(s):  
Magnetic Moment ◽  
Metal Ion ◽  
Free Ligand ◽  
Tetragonal Distortion ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Absorption Bands ◽  
Field Splitting ◽  
Zero Field Splitting Parameter ◽  
Splitting Parameter

<em>Some complexes of Ni(II) have been prepared with 2-thio-3-acetyl hydantoin (TAHN) and 2-formyl pyridine thiosemicarbazone (FPTS). On the basis of elemental analysis and molar conductivity, the complexes have been formulated as NiL<sub>2</sub>X<sub>2</sub>, where L = TAHN or FPTS and X = Cl<sup>–</sup>, Br<sup>–</sup>, NCS<sup>–</sup>, ClO<sub>4</sub><sup>–</sup>. The infrared spectra of complexes and free ligand reveal that the ligand TAHN is co-ordinated through sulphur and acetyl oxygen, while FPTS ligand co-ordinates through heterocyclic nitrogen and sulphur to Ni(II) metal ion. The magnetic moment of these complexes are found to be 3.20-3.25 B.M. The values are greater than value (2.828 B.M) corresponding to two unpaired electrons of a d<sup>8</sup>-system. The appearance of four absorption bands in their electronic spectra reveal, the tetragonal distortion in the octahedral symmetry of complexes. The zero field splitting parameter(D) and the other crystal field parameters like Dq<sub>(xy)</sub>, Dq<sub>(z)</sub>, Dt have been calculated. The results show that, the tetragonal distortion parameter (Dt) increases in the order of NCS<sup>– </sup>&lt; Cl<sup>–</sup> &lt; Br<sup>–</sup> while the zero field splitting parameter (D) also increases in the same order for both the planer ligands.</em>

Electron Spin Resonance of Cr3+ in K1–xTlxAl(SO4)2 · 12 H2O

2003 ◽  
Vol 58 (5-6) ◽  
pp. 303-305 ◽  
Author(s):  
V. K. Jain
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Metal Ion ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Trivalent Metal ◽  
Zero Field Splitting Parameter ◽  
Monovalent Ions ◽  
Spin Resonance ◽  
Splitting Parameter

The electron spin resonance (ESR) of Cr3+ in K1−xTlxAl(SO4)2·12H2O has been studied at 300 K and 9.45 GHz. The ESR spectrum for x between 30 and 90% shows several chromium complexes. The variation of the zero-field splitting parameter D suggests that monovalent ions play an important role in the trigonal distortion of the water octahedron around the trivalent metal ion in alums. - PASC: 76.30 F.

Mixed valency in polynuclear Mn II /Mn III , Mn III /Mn IV and Mn II /Mn III /Mn IV clusters: a foundation for high-spin molecules and single-molecule magnets

2007 ◽  
Vol 366 (1862) ◽  
pp. 113-125 ◽  
Author(s):  
Theocharis C Stamatatos ◽  
George Christou
Keyword(s):  
Single Molecule ◽  
Exchange Interactions ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Single Molecule Magnets ◽  
Zero Field Splitting Parameter ◽  
Jahn Teller ◽  
Splitting Parameter ◽  
Molecular Spin ◽  
Molecular Compounds

Mixed-valent Mn/O dinuclear and polynuclear molecular compounds containing Mn III are almost without exception trapped valence. Large differences between the strengths of the exchange interactions within Mn II Mn III , Mn III Mn III and Mn III Mn IV pairs lead to situations where Mn III Mn IV interactions, the strongest of the three mentioned and antiferromagnetic in nature, dominate the intramolecular spin alignments in trinuclear and higher nuclearity mixed-valent complexes and often result in molecules that have large, and sometimes abnormally large, values of molecular spin ( S ). When coupled to a large molecular magnetoanisotropy of the easy-axis-type (negative zero-field splitting parameter, D ), also primarily resulting from individual Jahn–Teller distorted Mn III centres, such molecules will function as single-molecule magnets (molecular nanomagnets). Dissection of the structures and exchange interactions within a variety of mixed-valent Mn x cluster molecules with metal nuclearities of Mn 4 , Mn 12 and Mn 25 allows a ready rationalization of the observed S , D and overall magnetic properties in terms of competing antiferromagnetic exchange interactions within triangular subunits, resulting spin alignments and relative orientation of Mn III JT axes. Such an understanding has provided a stepping stone to the identification of a ‘magnetically soft’ Mn 25 cluster whose groundstate spin S value can be significantly altered by relatively minor structural perturbations. Such ‘spin tweaking’ has allowed this cluster to be obtained in three different forms with three different groundstate S values.

SUPERPOSITION MODEL ANALYSIS FOR THE ZERO-FIELD SPLITTING OFMn2+IN SOME CRYSTALS

2006 ◽  
Vol 20 (30) ◽  
pp. 1917-1922 ◽  
Author(s):  
VIMAL KUMAR JAIN
Keyword(s):  
Lattice Relaxation ◽  
Zero Field ◽  
Superposition Model ◽  
Zero Field Splitting ◽  
Intrinsic Parameter ◽  
Order Zero ◽  
Field Splitting ◽  
Zero Field Splitting Parameter ◽  
Local Lattice ◽  
Splitting Parameter

The Newman superposition model has been applied to second-order zero-field splitting parameter [Formula: see text] taken from the literature for Mn2+in Hg(ClO4)2· 6 H2O , M ″ SiF6·6 H2O (M ″= Fe, Co, Zn ) and M ″ NbOF5·6 H2O (M ″= Co, Zn ). In the calculations, the local lattice relaxation has been taken into account. It is shown that nearly the same value of intrinsic parameter b2=-0.057(8) cm-1is obtained.

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

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