The magnetic susceptibility of ammonium pentafluoromanganate (III) has been determined in a temperature range of 4.2-300°K. The observed susceptibility to. temperature curve shows a broad maximum at 58°K due to antiferromagnetic interactions within -Mn-F-Mnchains and an additional sharp peak at 5.8°K attributable to weak ferromagnetic interaction between chains. Sodium and lithium pentafluoromanganates (111) are isostructural with the ammonium salt and show magnetic susceptibility vs. temperature curves resembling that of the ammonium salt except that the low-temperature peak is not observable above the liquid helium temperature.

The magnetic susceptibilities of CuX2L (X: halide ion, L: 1,2,4-triazole, pyridazine, phthalazine, 4-amino-1,2,4-triazole) conform to the linear Ising model or Heisenberg model, indicating the presence of linear magnetic chains in the crystals. Fermi contact shift observed in the broad-line PMR spectrum indicates the diffusion of a positive hole from a copper atom to the molecule of heterocycles. The magnitude of the exchange integrals is related to the spin densities on the atoms of the heterocycles.

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Tetramers consisting of two coupled dimers were classified as (a) linear, (b) cyclic, (c) rhombic, or (d) tetrahedral. The magnetic susceptibility for each tetramer model consisting of S=1/2 spins was obtained as an analytical equation. For the linear tetramer, the susceptibility equation was calculated numerically and compared with the observed values.