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CHAPTER 4. THE MAGNETICALLY ORDERED STATE
so that
where the intrasublattice- and intersublattice-molecular-field constants
and
are
defined as
In the paramagnetic regime, in the presence of a magnetic field H, the two sublattice
moments are given by
where
H = 0
represents the number of A atoms per mole of atoms of the material. A similar expression
holds for
A solution of Eqs. (4.4.10) and (4.4.11) with
and
can be found if
The corresponding temperature,
is now given by the relation
where the various types of constants C and N are given by Eqs. (4.4.8), (4.4.9), and (4.4.12).
For a given crystal structure, the number of nearest neighbors
known. In most cases, the values of g and J pertaining to the magnetic atoms are also
known. Equation (4.4.14) then gives essentially a relation between the magnetic-ordering
temperature and the magnetic-coupling constants
and
and
are
In deriving expressions for the total magnetization and sublattice magnetizations in the
magnetically ordered regime, we will assume that the moments of the A and B sublattices
are aligned strictly antiparallel. This is the case if
is the only nonzero molecular-field
constant or if
is large compared to
and
This assumption will be more
carefully examined later. The sublattice moments are then given by