Ferromagnetic Crystalline Anisotropy of MeFe2O4-Fe3O4 Ferrite Solid Solutions

The ferrite crystals of ternary system (Mn x Fe y Ni z )Fe 2 O 4 , where x + y + z =1, were grown by the Bridgman method in the air. According to the X-ray analysis, they have the spinel structure, except in the region near NiFe 2 O 4 , and their lattice constants depend linearly on the concentration: a =(8.518-0.125 y -0.176 z )±0.005 A. The ferromagnetic crystalline anisotropy was measured by the torque method in the temperature range between 90°K and 300°K. In normal specimens K 1 decreases with decreasing temperature. NiFe 2 O 4 –Fe 3 O 4 system shows an anomalous temperature dependence for a wide range of concentration: K 1 increases and changes its sign from negative to positive at low temperature. This will be due to the short range order of Fe 2+ and Fe 3+ at the octahedral site of the spinel lattice. If such an anomaly is subtracted, K 1 of the ternary system becomes maximum at a certain Fe 3 O 4 concentration. This can be attributable to the special contribution of Fe 2+ -ion. The crystal of (Zn 1- y Fe y )Fe 2 O 4 binary system were also investigated. They have the spinel structure with the lattice constant of a =(8.445-0.052 y )±0.005 A. The relation of the anisotropy constant to y also indicates the contribution of Fe 2+ mentioned above.