Layer Structures of Magnetic Oxides

In most of the ferromagnetic oxides, the anion lattices are constructed by piling up two dimentional trigonal lattice layers in succession. Metallic ions locate on the proper interstices of these anion layers, forming themselves also several kinds of layers. It has been shown that the crystal lattices of these oxides can be constructed uniquely by assuming 1) the layer structures outlined above, 2) requirement of minimizing the sum of electrostatic energy and interionic repulsive energy and, 3) the numbers of cations locating between two neighbouring anion layers are all the same, e. g. equal to that corresponding to the molecular ratio notwithstanding that there may be several kinds of cation structures as such inter-layer cation arragements. From this consideration, 13 M–O–M configurations are derived as possible configurations acting for the superexchange interaction in magnetic oxides. It is shown that the magnetic lattices also have layer structures.