The two-phase crystal structure and magnetic properties of the LaCo1−xFexO3−d system

The preparation conditions and magnetic properties of the La(Co1−x Fex)O3− d system of solid solutions were studied. Irrespective of synthesis conditions, the samples with x ≤ 0.15 were rhombohedral (space group R 3c ), and those with x ≥ 0.7, orthorhombic (space group Pnma). In the intermediate region of 0.15 < x < 0.7, the samples could be mixtures of rhombohedral and orthorhombic phases. Structural heterogeneity considerably decreased as the temperature of the synthesis increased or after annealing in a reducing medium. The samples containing more than 40% iron exhibited weak spontaneous magnetization, as is characteristic of weak ferromagnets. The magnetic properties and structure depend on the content of oxygen. A decrease in the concentration of oxygen sharply increases magnetic anisotropy; the coercive force is then close to 10 kOe, which is more than that known for other oxide systems. The magnetic properties are explained in terms of the model according to which Co3+ ions are in the low-spin state.