Effect of Copper Substitution on Fe3O4 Particles Prepared via Coprecipitation and Flux Methods

We investigated the effect of copper substitution on the magnetic and physical properties of Fe
₃
O
₄
prepared by coprecipitation and flux methods. The coprecipitation compositions were chosen according to the formula (Cu
_x
²⁺
Fe
_1-x
²⁺
) Fe
₂
³⁺
O
₄
, where x varied between 0 and 1. We found that the flux treatment method is ideal for growing large particles of sub-micrometer size. The size of the final particles obtained was in the range of 200-1500 nm, and the size decreased with increasing copper content. Cubic spinel structured Cu
_x
Fe
_3-x
O
₄
particles were obtained by conducting hydrogen gas reduction process at 380 °C-530 °C for 1-2 h after flux treatment. From x-ray diffraction patterns, all particles were determined to be cubic spinel without any sign of the tetragonal structure expected from the Jahn-Teller effect. For these cubic spinel particles, saturation magnetization was controlled at 25-86 Am
²
/kg, and the value decreased linearly with increasing copper content. The coercive force remained almost constant at 13.7-19.1 kA/m, independent of the copper content.