398
M. Reissner
Fig. 8.17 57 Fe Mössbauer spectra for CoGa 1.2 Fe 0.8 O 4 for selected fields at 4.2 K
From the obtained θ values it is seen that B int is parallel to B a , with deviations
of up to 18
◦ for A-sites. This deviations decrease with increasing Fe content x. For
the B-sites B int points in the direction antiparallel to B a with deviations up to 57
◦ .
This indicates that Fe moment on A-sites are antiparallel to the Fe-moment on the
B-sites. The fact that B int increases with x and θ decreases with x points to an
increase in coupling strength with increasing Fe content. Assuming that there is a
direct proportionality between internal hyperfine field B int and the magnetic moment,
the fact that B int is larger on B-sites than on A-sites indicates that the resultant B int
is antiparallel to B a and therefore the overall moment, which is antiparallel to the
internal field, is parallel to the applied field. This is in good agreement with the fact
that in dc magnetic measurements a ferromagnetic like behaviour is obtained [40].
M. Reissner
Fig. 8.17 57 Fe Mössbauer spectra for CoGa 1.2 Fe 0.8 O 4 for selected fields at 4.2 K
From the obtained θ values it is seen that B int is parallel to B a , with deviations
of up to 18
◦ for A-sites. This deviations decrease with increasing Fe content x. For
the B-sites B int points in the direction antiparallel to B a with deviations up to 57
◦ .
This indicates that Fe moment on A-sites are antiparallel to the Fe-moment on the
B-sites. The fact that B int increases with x and θ decreases with x points to an
increase in coupling strength with increasing Fe content. Assuming that there is a
direct proportionality between internal hyperfine field B int and the magnetic moment,
the fact that B int is larger on B-sites than on A-sites indicates that the resultant B int
is antiparallel to B a and therefore the overall moment, which is antiparallel to the
internal field, is parallel to the applied field. This is in good agreement with the fact
that in dc magnetic measurements a ferromagnetic like behaviour is obtained [40].