8 Mössbauer Spectroscopy in External Magnetic Fields
399
Fig. 8.18 Measured
hyperfine field B h f over
applied field B a for
CoGa 1.2 Fe 0.8 O 4
Table 8.1 Mean values of measured hyperfine field B h f , angle between B h f and applied field B a
and calculated internal field B int for both A- and B-sites for different B a and Fe concentration x [41].
Reprinted by permission from Springer: Hyperfine Interactions, High field Mössbauer investigations
of CoGa 2−x Fe x O 4 spinels, M. Reissner, W. Steiner, Z. Seidov, G. Sultanov, copyright (2002)
x
1,0
0,8
0,3
0,2
B a
B h f θ
B int B h f θ
B int B h f θ
B int B h f θ
B int
[T]
[T]
[°]
[T]
[T]
[°]
[T]
[T]
[°]
[T]
[T]
[°]
[T]
A
0
50.1
49.0
46.8
46.2
4
53.2 12
49.1 51.7 18
47.9 49.2 18
45.4 49.2 18
48.0
9
58.4 12
49.2 56.9 18
48.4 53.7 18
45.2 54.1 18
45.6
13.5 62.9 5
49.6 61.4 18
48.7 58.4 18
45.8
B
0
53.3
52.0
51.6
50.5
4
49.8 210 53.5 49.5 230 52.2 49.0 232 51.6 48.1 237 50.4
9
45.0 205 53.3 44.8 218 52.2 44.7 230 51.0 43.0 230 49.3
13.5 40.4 202 53.2 40.4 214 52.1 40.2 225 50.7
With increasing x the number of iron atoms on A-sites decrease, whereas it increases
on B-sites. The ratio for iron on A-sites (y) and Fe on B-sites (z) increases with x.
It is 0.25, 0.33, 0.54, and 0.64 for x = 0.2, 0.3, 0.8, and 1.0, respectively. The same
tendency was found by the X-ray investigations [38]. The application of external
fields allowed to show that the different field dependence of the two components
found in the spectra proves that both A- and B-sites are occupied by iron atoms.
The different intensities of these two components prove that the samples are partial
inverse spinels. A antiferromagnetic coupling is found between Fe on A- and Bsites. The values of the internal fields are around 10% higher for the iron atoms at
the B-sites and are only mildly dependent on x.
399
Fig. 8.18 Measured
hyperfine field B h f over
applied field B a for
CoGa 1.2 Fe 0.8 O 4
Table 8.1 Mean values of measured hyperfine field B h f , angle between B h f and applied field B a
and calculated internal field B int for both A- and B-sites for different B a and Fe concentration x [41].
Reprinted by permission from Springer: Hyperfine Interactions, High field Mössbauer investigations
of CoGa 2−x Fe x O 4 spinels, M. Reissner, W. Steiner, Z. Seidov, G. Sultanov, copyright (2002)
x
1,0
0,8
0,3
0,2
B a
B h f θ
B int B h f θ
B int B h f θ
B int B h f θ
B int
[T]
[T]
[°]
[T]
[T]
[°]
[T]
[T]
[°]
[T]
[T]
[°]
[T]
A
0
50.1
49.0
46.8
46.2
4
53.2 12
49.1 51.7 18
47.9 49.2 18
45.4 49.2 18
48.0
9
58.4 12
49.2 56.9 18
48.4 53.7 18
45.2 54.1 18
45.6
13.5 62.9 5
49.6 61.4 18
48.7 58.4 18
45.8
B
0
53.3
52.0
51.6
50.5
4
49.8 210 53.5 49.5 230 52.2 49.0 232 51.6 48.1 237 50.4
9
45.0 205 53.3 44.8 218 52.2 44.7 230 51.0 43.0 230 49.3
13.5 40.4 202 53.2 40.4 214 52.1 40.2 225 50.7
With increasing x the number of iron atoms on A-sites decrease, whereas it increases
on B-sites. The ratio for iron on A-sites (y) and Fe on B-sites (z) increases with x.
It is 0.25, 0.33, 0.54, and 0.64 for x = 0.2, 0.3, 0.8, and 1.0, respectively. The same
tendency was found by the X-ray investigations [38]. The application of external
fields allowed to show that the different field dependence of the two components
found in the spectra proves that both A- and B-sites are occupied by iron atoms.
The different intensities of these two components prove that the samples are partial
inverse spinels. A antiferromagnetic coupling is found between Fe on A- and Bsites. The values of the internal fields are around 10% higher for the iron atoms at
the B-sites and are only mildly dependent on x.