Chemistry Reference
In-Depth Information
1.00
0.95
-10
-5
0
5
10
Velocity,
v
/ mm s
-1
Fig. 1.8
57
Fe Mossbauer spectrum obtained from Nd
2
Fe
14
B at room temperature. Spectrum
consists of six different sextets that correspond to
57
Fe at six different atomic sites. Hyperfine
interaction parameters like H
hf
, DE
q
, IS and relative aria contribution can be determined from the
analysis of the spectrum
Figure
1.7
shows the calculated Mössbauer spectra as a function of relaxation
time s assuming the magnitude of saturated hyperfine field and the quadrupole
splitting are same as observed for a-FeOOH.
1.3 Typical Example of the Application to the Material
Research
In this section, a typical example of the application to the material research is
presented. From the Mössbauer spectrum obtained from multiple phase material in
which the
57
Fe Mössbauer active atoms have several different atomic sites, one can
distinguish the hyperfine parameters for each of the different atomic sites. Figure
1.8
shows a Mössbauer spectrum obtained from Nd
2
Fe
14
B at room temperature.
Nd
2
Fe
14
B has 6 different crystallographic sites for Fe and is recognized as an
important material for the super-strong permanent ferromagnet. From this absorp-
tion spectrum, the ratio of site occupation, the isomer shift value, the quadrupole
splitting and the magnitude of the hyperfine magnetic field (proportional to atomic
magnetic moment) of each site have been determined separately.
1.4 Nuclear Resonance with Synchrotron Radiation
In previous section we treat the Mössbauer spectroscopy using a radioactive c-ray
source, which has an extremely narrow line width of the order of 10
-9
eV in the case
of
57
Fe resonance. Mössbauer effect is a recoilless emission and a recoilless resonant
absorption of low energy c photons in a combination with source and absorber nuclei.
