Alloying of Fe3O4 and Co3O4 to develop Co3xFe3(1−x)O4 ferrite with high magnetic squareness, tunable ferromagnetic parameters, and exchange bias

• The ferrite Co3xFe3(1−x)O4 has been synthesized by alloying Fe3O4 and Co3O4.
• The correlation between structural phase and ferromagnetism has been studied.
• The ferrite exhibited tunable ferromagnetic parameters with high squareness.
• Unusual features, e.g., exchange bias, field controlled domain motion, studied.
• The study is important for developing next generation magnetic ferrites.

Ferromagnetic (FM) Fe3O4 and antiferromagnetic (AFM) Co3O4 has been alloyed to form the ferrite composition Co3xFe3(1−x)O4 (x = 0.1, 0.3, 0.5). Three different routes, viz., mechanical alloying at room temperature, annealing of the mechanically alloyed sample and solid state sintering, have been followed to develop the ferrite. X-ray diffraction pattern showed incomplete alloying in as milled samples. Single phased cubic spinel structure has formed after annealing of the mechanical alloyed samples at 950 °C, and also in solid state routed samples. The single phase has not formed for the samples at low Co content (x = 0.1), but the single phased cubic spinel structure is stabilized for the higher value of Co content (x = 0.3, 0.5). All samples showed FM loop at room temperature. The FM parameters (magnetization, squareness, coercivity) of the mechanically alloyed samples after annealing at 950 °C showed higher values in comparison with as milled and solid state routed samples with similar composition. Amongst the studied samples, the composition Co0.9Fe2.1O4 (for x = 0.3) exhibited better FM properties in comparison with samples for the compositions x = 0.1 and 0.5. The present work highlighted few more unusual ferromagnetic features, e.g., different types of exchange bias effect, applied field controlled freezing of the ferromagnetic domains, tailoring of the Verwey transition of Fe3O4 in the presence of AFM Co3O4, and field driven de-pinning of the domain wall motion at lower temperature that can be manipulated for developing next generation advanced magnetic ferrites.

ZFC and FC loop for M3 sample at 10 K (a), A1 sample (b), B3 sample (c) and A5 sample (d).Figure optionsDownload as PowerPoint slide