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Magnetic Structure Factors
The magnetic structure factor M(k) can be defined as
the Fourier transform of
the magnetisation distribution.
The intensity of neutron scattering is proportional to the square
of the component of M(k)perpendicular to the scattering
vector k. This is the magnetic interaction vector
. Thus
Using the description of a magnetic structure just given the magnetic
structure factor is written:
is the magnetic form factor and
the Fourier transform of the
modulating function
. The sum over the lattice vectors is
zero unless
where g is a reciprocal lattice vector. At
present CCSL only recognises sinusiodal modulations so that
unless
. The rest of the equation defines the unit cell magnetic structure
factor; its projection on the plane perpendicular to the scattering vector is
the quantity calculated by the magnetic structure factor routines
FMCALC and
LMCALC.
P.J. Brown - Institut Laue Langevin, Grenoble, FRANCE. e-mail brown@ill.fr