Mössbauer study of the hyperfine magnetic field and electric field gradient at Fe sites in synthetic diamond.
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Date
1992
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Abstract
Mossbauer Spectroscopy has been used to investigate the
site of Fe inclusions in a suite of synthetic diamonds (de
Beers MDAS). Information on the hyperfine magnetic fields
and electric field gradients at Fe sites in the diamond
grains were obtained from Mossbauer Spectroscopy of diamond
grains ranging in size from 25 to 250 um. The Fe inclusions
in these samples resulted from the synthesis of the diamond
grains in which Fe was used as a catalytic solvent. The
Mossbauer measurements were carried at room temperature
with a constant acceleration spectrometer operating in
transmission geometry.
The samples with the largest grain size of 180-250 um gave
a well defined six component magnetically split spectrum,
similar to the Zeeman split sextet obtained for natural
iron. As the grain sizes decreased the intensity of
the magnetically split components became greatly reduced
and a strong paramagnetic component appeared. At grain
sizes 105-45 um the spectra are dominated by a central
single line with some evidence of an asymmetric doublet.
For the finest grain size 38-25 um, the reappearance of
the six magnetic hyperfine splitting components together
with the strong central single paramagnetic component was
observed.
The change in the Mossbauer patterns observed with decreasing
grain size suggest that a rapid phase transition of the
Fe inclusions from ferromagnetic to superparamagnetic
takes place.
The analysis of Mossbauer spectra yielded a value of the
hyperfine magnetic field of Bhf = -32.4(4) T and an
electric field gradient in the range of Vzz = 1.4(4) 1.8(
7) X 10'8 V.cm- 2 at the site of the probe s7Fe
nucleus. These values compare favourably with other
measurements.
Description
Thesis (M.Sc.)-University of Durban-Westville, 1992.
Keywords
Theses--Physics., Mossbauer spectroscopy., Mossbauer effect.