Antiferromagnetic exchange constants

The antiferromagnetic exchange constant was probably overestimated by not taking into account the strong spin-orbit coupling characteristic of the HS-Co ions (247). 

Figure 2 Plot of calculated versus estimated antiferromagnetic exchange constants for the complexes in aprotic solvents (solid circles) and the complexes in aqueous solutions (solid squares). The equation for the line is /est=l-5, /af —260, 7 = 0.86 (reproduced with permission from ref. 38 1998, American...

In Table 1, the perchlorate salt of [ Ru(NH3)5 2(m-1)]" possesses a considerably larger antiferromagnetic exchange constant compared to the analogous tosylate salt. It seems probable that this arises because of a difference in the crystal structures. Indeed, as shown below, outer-sphere perturbations can significantly reduce antiferromagnetic exchange in these complexes. 

EPR due to pairs of exchange coupled Cu + antiferromagnetic exchange constant 2 J /hc= ions occupying nearest-neighbour typel sites =(33 l)cm determined ... 

The structure of the pyrazine complex was suggested to contain polymeric square planar cations with bridging pyrazines and the magnetic properties (300-80K) were interpreted in terms of an antiferromagnetic exchange interaction. A Curie-Weiss constant of 84 K was calculated. At room temperature, the magnetic moment was found to be 1.61 BM. 

Margraf D., Cekan, P., Prisner, T. F., Sigurdsson, S. T., and Schiemann, O. (2009). Ferro-and antiferromagnetic exchange coupling constants in PELDOR spectra. Phys. Chem. Chem. Phys. 11, 6708—6714. 

Neutron diffraction experiments have confirmed that KCrF3 exhibits antiferromagnetism of type A with the spins lying in the pseudo-tetragonal (001) plane41) (TN = 40 K 6P = + 5 K42)). The exchange constants calculated on the basis of the molecular field theory have the same order of magnitude within and between two layers J3/k = 1.4 K and J2/k = - 2.2 K42). 

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