Spin dimer, electronic band structure and classical spin analyses of spin exchange interactions and ordered magnetic structures of magnetic solids

We reviewed briefly how spin dimer, electronic band structure and classical spin analyses are employed to describe spin exchange interactions and ordered magnetic structures of magnetic solids. It was shown that super-superexchange interactions are crucial in forming strongly interacting spin units of magnetic solids and hence in determining their magnetic properties, and that incommensurate magnetic superstructures are readily described by a Heisenberg spin Hamiltonian using the classical spin approximation. We probed the weak ferrimagnetism of monoclinic Fe2(SO4)3 in terms of spin dimer and mean-field-theory analyses to explain both the ordered magnetic structure and the sublattice magnetization. The classical spin and quantum mechanical descriptions of geometric spin frustration were compared to clarify their differences.