Neutron Scattering

So far we have discussed the nuclear and magnetic scattering separately.
in general there are possible non-zero matrix elements for both contributions .
However,
Therefore
interference phenomena may occur but only in the non-spin flip channel . In order to
maximize the magnetic signal one chooses the magnetization perpendicular to the scattering
plane .
In cases where the magnetic scattering amplitude is much weaker than the
nuclear amplitude the interference term may be large compared with the pure magnetic
intensity .
Since the polarization of the scattered beam is not changed, and thus already
determined we do not need to perform the polarization analysis in the experiment .
A
useful application of this effect is the determination of the distribution of magnetization
densities .
For instance, the form factor of chromium can be measured in the paramagnetic
phase, inducing a magnetization by an external magnetic field, as shown in Fig . 4 .12 .
D3
a
é
ô
v
08
0.6
0 .4
o Stassis
. . . . .
3d spi
. . . . .. . . 3d orbital
40% spin + 60% orbital
â
0.2
0 .0
......... . . . . .
a
00 0.2 0 .4 0.6 0.8 1 .E
1f2d (Ä- t )
Figure 4 .12 : Induced magnetic form factor of Cr at a field of 4 .6 Tesla. Open and filled
circles are experimental data, lines denote theoretical calculations for spin- orbital-, and
total magnetic moments [13] .
4- 17