Super-exchange coupling constants

The two spins 5a and 5b are assumed to be local, associated with the two sites a and b, respectively. The parameter J is the so-called exchange-coupling constant, which expresses the strength of the (super)exchange interaction between the... 

Magnetic susceptibility measurements [77] show that the MnF4 obtained using KrF2 follows the Curie-Weiss law (Weiss constant 9 = 10 K) with ef-f=3.85 appropriate for three unpaired spins. Since the Weiss constant is small the super exchange coupling Mn(IV)—F—Mn(IV) must be weak. 

Table 8 Calculated direct Jd(K) and super-exchange Jse(K) coupling constants, fluctuation-corrected mean field Neel temperature, (K) and Bloch constant in MnO...

By analogy with non-exchanging spin systems the superoperators which commute with both the super-Hamiltonian and the superoperator T in composite Liouville space may be called the constants of the motion. In some instances there may be additional constants of the motion which result from the conservation of some molecular symmetry in the exchange, from the magnetic equivalence of some nuclei, and from weak spin-spin coupling. (15, 52) For example,... 

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