Antiferromagnetic mechanism

There is no Anderson s antiferromagnetic mechanism (or kinetic exchange ) in such magnetic systems. 

Figure 6.6 Interaction between magnetic impurities through RKKY mechanism. Interaction between the magnetic impurity at the origin 0 and that at a distance r = 0/4 is antiferromagnetic interaction with a second impurity at r = OB is ferromagnetic. It is seen that the interaction is oscillatory and dies away slowly as the inverse cube of r.

Next, we discuss the magnetic behaviour of the materials described here as B/U is varied. The moment at T=0 in the antiferromagnetic lattice and Goodenough s (1971) conjecture for the Neel temperature are shown in Fig. 4.12. There exists at present no good theoretical description of the way TN drops as we go towards the value of B/U where the moments vanish. Near this value we do not expect an entropy /cBln 2 on going through the Neel point. With small values of there is a quantum-mechanical resonance between the two directions of the moment, and the moments on a given atom are nearly equal, so < z> is small at TN they become equal. The susceptibility should appear as in Fig. 4.13. 

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