Synthesis of Copper and Lithium Copper Ferrites as High Magnetization Materials

Abstract

The ferrite with composition Cu_0.5Fe_2.5O₄ was heat treated in air and in reducing atmospheres to different temperatures within the solid solution region confirmed by dynamic high-temperautre x-ray characterization. The samples were quenched in oil and air, and lattice parameter, Curie temperature, and saturation magnetization measurements were completed. The magnetization measurements for these samples showed a maximum 4πM_s of 0.7729 and 0.5426 T at 10 and 300 K, respectively. The cationic distribution based on the low-temperature 4πM_s measurements is (Cu⁺_0.24Fe³⁺_0.76)A[Cu⁺_0.26Fe³⁺_1.74]_BO₄ → 4.9 µ _B. X-ray-pure Cu_0.5Fe_2.5O₄ samples were also synthesized by slow cooling from the formation temperature to 900 °C in a reducing atmosphere. A temperature–P_O2 diagram for the stability of Cu_0.5Fe_2.5O₄ under the conditions of the experiment was determined. Low-temperature 4πM_s measurements did not indicate an increase in the Cu⁺ A site occupancy for the samples cooled to 900 °C in a reducing environment above those samples that were quenched from high temperature. Curie temperatures for all Cu_0.5Fe_2.5O₄ samples ranged from 348 to 369 °C. Lithium additions (0.1 mol/unit formula) to copper ferrite Li_0.1Cu_0.4Fe_2.5O₄ decreased the room-temperature 4πM_s values to 0.5234 T with a corresponding decrease in the 10 K measurements to 0.7047 T. From the low-temperature magnetization measurements, the distribution was (Cu⁺_0.15Fe3⁺_0.85)A[Cu⁺_0.25Li⁺_0.1Fe³⁺_1.65]_BO₄ → 4.48 µ _B.