Physics of Magnetism

36 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