7.2.4 Hyperfine parameters as determined from nuclear gamma resonance studies

The chemical environment of Cu2+ions adsorbed in tannin-formaldehyde resins ofAcacia mearnsiibark extracts, prepared from polybutene, is investigated by EPR spectroscopy at 300 K. The spectrum is simulated considering two isolated axial Cu(II) species (Species 1:A∥=16.50(5) mT,A⊥=1.20(10) mT,g∥=2.28(1), andg⊥=2.08(1); Species 2:A∥=15.00(5) mT,A⊥=1.50(10) mT,g∥=2.32(1), andg⊥=2.05(2)), superposed to a broad line (giso=2.14(1); linewidth = 30.0(5) mT) assigned to Cu(II) aggregates. Measurements at 77 K did not improve spectral resolution. Heating at 413 K changes the hyperfine parameters of Species 2 (A∥=14.20(5) mT,A⊥=1.20(10) mT,g∥=2.33(1), andg⊥=2.07(2)) and slightly modifies the parameters of the broad line (giso=2.11(2); linewidth = 40.00(50) mT) but does not change Species 1, assigned to Cu(II) species immobilized into resin pores in cathecolate-type coordination sites. Species 2 is assigned to Cu(II) species immobilized at the outer resin surface. Upon extended heating, a reversible formation of semiquinone-type paramagnetic radicals (giso=2.0037(1)) is observed, assigned to the partial collapse of the resin polymeric network.

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Mössbauer Spectroscopy — Nuclear Gamma Resonance

Catalyst Characterization - Fundamental and Applied Catalysis ◽

10.1007/978-1-4757-9589-9_8 ◽

1994 ◽

pp. 215-246 ◽

Cited By ~ 1

Author(s):

P. Bussière

Keyword(s):

Mössbauer Spectroscopy ◽

Mossbauer Spectroscopy ◽

Mößbauer Spectroscopy ◽

Nuclear Gamma Resonance

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Structure, Magnetic Properties and Hyperfine Parameters of Nd-Substituted Ni-Fe-Ga Heusler Alloys

MRS Advances ◽

10.1557/adv.2017.70 ◽

2017 ◽

Vol 2 (25) ◽

pp. 1341-1346

Author(s):

Monica Sorescu ◽

Felicia Tolea ◽

Mihaela Valeanu ◽

Mihaela Sofronie

Keyword(s):

Melt Spinning ◽

Magnetic Measurements ◽

Heusler Alloys ◽

Hyperfine Magnetic Field ◽

Rapid Quenching ◽

Linear Least Squares ◽

X Ray Diffraction ◽

Hyperfine Parameters ◽

X Ray ◽

Field Distributions

ABSTRACTSamples of Ni57-xNdxFe18Ga25 with x=2 and 4 were prepared in ribbon form by rapid quenching via melt spinning route. The samples were analyzed by X-ray diffraction (XRD), magnetic measurements and Mössbauer spectroscopy, both in the as-quenched form and after thermal annealing at 900 oC for 2 min and 400 °C for 2 hours. For x=2 the Nd atoms are completely dissolved in the Ni-Fe-Ga matrix, while for x=4 the additional occurrence of the secondary 2:17 phase could be resolved. These findings were supported by the analysis of hyperfine magnetic field distributions obtained from the non-linear least-squares fitting of the Mössbauer spectra.

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