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

Structural phase transition in Zn1.98Mn0.02P2O7: EPR evidence for enhanced line broadening and large zero-field splitting parameter in high temperature phase

2013 ◽  
Vol 28 (22) ◽  
pp. 3157-3163 ◽  
Author(s):  
Santosh K. Gupta ◽  
Ramakant Mahadeo Kadam ◽  
Pradeep Samui ◽  
Krishnan Kesavaiyer ◽  
Venkataraman Natarajan ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Zero Field ◽  
Line Broadening ◽  
Zero Field Splitting ◽  
Zero Field Splitting Parameter ◽  
Splitting Parameter ◽  
Image Position

Abstract

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.

Electron Paramagnetic Resonance and X-ray Studies of the Phase Transformation in Pb3P2O8

1975 ◽  
Vol 53 (1) ◽  
pp. 42-51 ◽  
Author(s):  
H. N. Ng ◽  
C. Calvo
Keyword(s):  
Rhombohedral Phase ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Paramagnetic Resonance ◽  
Field Splitting ◽  
Space Group ◽  
X Ray ◽  
Monoclinic Cell

The compound Pb3P2O8 has a low temperature monoclinic phase with space group C2/c and a high temperature phase with space group [Formula: see text], both with two crystallographically inequivalent cationic sites. X-ray data taken at five temperatures have indicated that an F-centered monoclinic cell is developed prior to its transition to the rhombohedral phase. The EPR spectra at room temperature show that Mn2+ substitutes only at the cationic site on the twofold axis. A phase transition occurs at 185 °C and approaching this temperature from below the magnetic axes in the ac plane rotate continuously, by about 40°. At 185 °C the Z axis coincides with the c axis of the hexagonal cell (a* axis of the monoclinic cell). The crystal field splitting parameter b20 increases from −423 G to −222 G while b22 goes from 280 G to zero. A model based on the theory of Blume and Orbach for the zero-field splitting and with point charges as the source of the electric field is used to relate the EPR parameters to the atomic displacements.

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.

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.

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.

EPR Studies of Cr3+ and Fe3+ in Host Crystals with Langbeinite Structure

1996 ◽  
Vol 51 (10-11) ◽  
pp. 1123-1133
Author(s):  
J. Kastner ◽  
B. D. Mosel ◽  
W. Müller-Warmuth
Keyword(s):  
Charge Compensation ◽  
Qualitative Description ◽  
Ligand Field ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Temperature Dependent ◽  
Paramagnetic Resonance ◽  
Local Relaxation ◽  
Hamiltonian Parameters ◽  
Electron Paramagnetic

Abstract Electron paramagnetic resonance (EPR) spectra of trivalent chromium and iron ions have been investigated in host crystals of double sulfates with langbeinite structure, A2B2(SO4)3 , with A = NH4+, Rb+, Tl+ and B = Cd2+, Mg2+. In most cases, single crystals could be grown, and the spin Hamiltonian parameters have been determined from the rotational diagrams. Powder spectra were analyzed and simulated as well. Three centres of axial symmetry with different zero field splittings have been observed for Cr3+, and two for Fe3+. The trivalent impurity ions have been shown to occupy divalent lattice sites substitutionally, but the environments are different depending on the structure and the mechanism of charge compensation. A qualitative description of the incorporation of dopants has been possible on this basis, taking into account the local relaxation and the ligand field stabilization effects. Temperature dependent single crystal and powder measurements have provided information on the zero field splitting and phase transitions.

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