A new class of compounds with unusual magnetic behaviour: quasi-one-dimensional complex oxides of the A_3n+3mA′_nB_3m+nO_9m+6n family

The results of investigations into the conditions of synthesis, structure and magnetic properties of quasi-one-dimensional perovskite-like complex oxides of the A_3n+3mA′_nB_3m+nO_9m+6n family (A = Ca, Sr, Ba; A′ = Cu, Ni, Co, Zn, Mg; B are platinum metals, Mn and other d and p elements) are generalised. It is shown that the low-dimensional structure of the compounds is determined by the presence of isolated chains consisting of octahedra occupied by the B cations and trigonal prisms with the A′-cations which alternate in various ratios. The reasons for the formation of incommensurate compounds and the methods for the refinement of their structures are considered. It is demonstrated that the presence of transition metals and the quasi-one-dimensional structure are responsible for the high anisotropy of the magnetic properties of the A_3n+3mA′ _nB_3m+nO_9m+6n oxides and, in particular, for the preservation of the intrachain exchange interactions to relatively high temperatures and the low temperatures of three-dimensional magnetic ordering.