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Cobalt ferrite is a semi-hard ferrite with the chemical formula of CoFe₂O₄ (CoO·Fe₂O₃). The substance can be considered as between soft and hard magnetic material and is usually classified as a semi-hard material.

Applications

It is mainly used for its magnetostrictive applications like sensors and actuators thanks to its high saturation magnetostriction (~200 ppm). CoFe₂O₄ has also the benefits to be rare-earth free, which makes it a good substitute for Terfenol-D. Moreover, its magnetostrictive properties can be tuned by inducing a magnetic uniaxial anisotropy. This can be done by magnetic annealing, magnetic field assisted compaction, or reaction under uniaxial pressure. This last solution has the advantage to be ultra fast (20 min) thanks to the use of spark plasma sintering. The induced magnetic anisotropy in cobalt ferrite is also beneficial to enhance the magnetoelectric effect in composite.

Cobalt ferrite can be also used as electrocatalyst for oxygen evolution reaction and as material for fabricating electrodes for electrochemical capacitors (also named supercapacitors) for energy storage. These uses take advantage of the redox reactions occurring at the surface of the ferrite. Cobalt ferrite prepared with controlled morphology and size to enhance the surface area, and thus the number of active sites, has been published. One disadvantage of the cobalt ferrite for some applications is their low electrical conductivity. Nanostructures of cobalt ferrite with different shape can be synthesized on conducting substrates, such as reduced graphene oxide, to alleviate this disadvantage.

See also

• Ferrite

References

1. Hosni (2016). "Semi-hard magnetic properties of nanoparticles of cobalt ferrite synthesized by the co-precipitation process". Journal of Alloys and Compounds. 694: 1295–1301. doi:10.1016/j.jallcom.2016.09.252.
2. Olabi (2008). "Design and application of magnetostrictive materials" (PDF). Materials & Design. 29 (2): 469–483. doi:10.1016/j.matdes.2006.12.016.
3. Sato Turtelli; et al. (2014). "Co-ferrite – A material with interesting magnetic properties". IOP Conference Series: Materials Science and Engineering. 60: 012020. doi:10.1088/1757-899X/60/1/012020.
4. J. C. Slonczewski (1958). "Origin of Magnetic Anisotropy in Cobalt-Substituted Magnetite". Physical Review. 110 (6): 1341–1348. doi:10.1103/PhysRev.110.1341.
5. Lo (2005). "Improvement of magnetomechanical properties of cobalt ferrite by magnetic annealing". IEEE Transactions on Magnetics. 41 (10): 3676–3678. doi:10.1109/TMAG.2005.854790. S2CID 45873667.
6. Wang (2015). "Magnetostriction properties of oriented polycrystalline CoFe2O4". Journal of Magnetism and Magnetic Materials. 401: 662–666. doi:10.1016/j.jmmm.2015.10.073.
7. Aubert, A. (2017). "Uniaxial anisotropy and enhanced magnetostriction of CoFe2O4 induced by reaction under uniaxial pressure with SPS". Journal of the European Ceramic Society. 37 (9): 3101–3105. arXiv:1803.09656. doi:10.1016/j.jeurceramsoc.2017.03.036. S2CID 118914808.
8. Aubert, A. (2017). "Enhancement of the Magnetoelectric Effect in Multiferroic CoFe2O4/PZT Bilayer by Induced Uniaxial Magnetic Anisotropy". IEEE Transactions on Magnetics. 53 (11): 1–5. arXiv:1803.09677. doi:10.1109/TMAG.2017.2696162. S2CID 25427820.
9. ^ Ortiz-Quiñonez, Jose-Luis; Das, Sachindranath; Pal, Umapada (October 2022). "Catalytic and pseudocapacitive energy storage performance of metal (Co, Ni, Cu and Mn) ferrite nanostructures and nanocomposites". Progress in Materials Science. 130: 100995. doi:10.1016/j.pmatsci.2022.100995.

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