Spin Dimer Analysis of the Spin Exchange Interactions of the Vanadium Oxides AV4O9 (A=Ca, Sr, Cs2, NH2(CH2) 4NH2)

The spin exchange interactions of the vanadium oxides AV4O9 (A=Ca, Sr, Cs2, and NH2(CH2)4NH2) were examined by calculating the spin orbital interaction energies of their spin dimers based on the extended Hückel method. The temperature Tmax at which the magnetic susceptibility maximum occurs in AV4O9 (A=Ca, Sr, Cs2, and NH2(CH2)4NH2) shows a wide variation (from 30 to 600 K) and increases in the order [NH2(CH2)4NH2]V4O9