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Magnetic Relaxation Effects in the Mössbauer Spectrum of Fe 2+ in Gillespite
Author(s) -
Srivastava K. K. P.,
Mishra S. N.
Publication year - 1982
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221130109
Subject(s) - relaxation (psychology) , paramagnetism , condensed matter physics , ion , spin–lattice relaxation , chemistry , mössbauer spectroscopy , spin–spin relaxation , hyperfine structure , mössbauer effect , nuclear magnetic resonance , crystallography , atomic physics , physics , psychology , social psychology , organic chemistry
Abstract The Mössbauer spectrum of paramagnetic 57 Fe 2+ (3d 6 , 5 D) ions of the mineral gillespite (BaFeSi 4 O 10 ) is found to show the effect of magnetic relaxation (i.e. relatively slow electronic spin relaxation rate) from 4.2 to 300 K. It is widely believed that ferrous ions are strongly coupled to lattice vibrations and consequently any spin relaxation effect on their Mössbauer spectra may be observed at very low temperatures only when the spin—lattice relaxation rates will be relatively small. In view of this the observed electronic spin relaxation behaviour of Fe 2+ in gillespite is very unusual and rather surprising. A theoretical analysis is made to identify the dominant relaxation mechanism. A detailed analysis of the electronic eigenstates and their relaxation properties shows that in the case of gillespite the spin—spin relaxation is more dominant than the spin—lattice relaxation, which is rather unusual for Fe 2+ ions. On this basis the observed magnetic relaxation behaviour of the Mössbauer spectra is consistently explained. It appears that the spin—lattice relaxation rate depends as much on the magnitude of the crystal field splitting as on the symmetry of the crystal field interaction itself as earlier suggested from the study of the low temperature Mössbauer spectra of Fe 2+ in various carbonates.