Reduced magnetization, surface ferric

In the following discussion, we treat the surface effect on the basis of the Weiss field (molecular field) approximation (17-19), assuming no relaxation (fluctuation of the electron spins). In the treatment, the reduced magnetization m (magnetization at a certain temperature divided by that at OK) of the surface ferric ions at temperature T K is described by... 

In the simplest case in which the trivalent Fe-57 ions are completely incorporated into the cooperative antiferromagnetic system of the bulk substrate, the Fe-57 ions are expected to align parallel or antiparallel to the magnetic ions of the substrate in a similar manner as the ferric ions of the substrate. When the trivalent Fe-57 ions are on the surface, however, their magnetization is considered to be reduced to some extent due to reduction in the number of neighboring magnetic metal ions interacting with them. 

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