{{Chembox | IUPACName = cobalt(2+);iron(3+);oxygen(2-) |Section1={{Chembox Identifiers | PubChem = 44602546 | CASNo = 12052-28-7 | ChemSpiderID = 21241477 | EINECS = 234-992-3 | StdInChI=1S/Co.2Fe.4O/q+2;2*+3;4*-2 | StdInChIKey = MMOVVVBHLUGHGW-UHFFFAOYSA-N | SMILES = [O-2].[O-2].[O-2].[O-2].[Fe+3].[Fe+3].[Co+2] }} |Section2={{Chembox Properties |Co=1|Fe=2|O=4 }} | Section7 = {{Chembox Hazards | GHS_ref = <ref>{{Cite web |last=PubChem |title=Cobalt iron oxide (CoFe2O4) |url=https://pubchem.ncbi.nlm.nih.gov/compound/44602546 |access-date=2026-03-11 |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref> | GHSPictograms = {{GHS06}}{{GHS08}} | GHSSignalWord = Danger | HPhrases = {{H-phrases|H317|H330|H334|H360F|H372}} | PPhrases = {{P-phrases|P203|P233|P260|P264|P270|P271|P272|P280|P284|P302+P352|P304+P340|P316|P318|P319|P320|P321|P333+P317|P342+P316|P362+P364|P403|P403+P233|P405|P501}} }} }} '''Cobalt ferrite''' is a semi-hard ferrite with the chemical formula CoFe<sub>2</sub>O<sub>4</sub> (CoO·Fe<sub>2</sub>O<sub>3</sub>). The substance can be considered as between a soft and hard magnetic material and is usually classified as a semi-hard material.<ref>{{cite journal|last1=Hosni|title=Semi-hard magnetic properties of nanoparticles of cobalt ferrite synthesized by the co-precipitation process|journal=Journal of Alloys and Compounds|volume=694|pages=1295–1301|date=2016|doi=10.1016/j.jallcom.2016.09.252}}</ref>
== Uses == Cobalt ferrite is mainly used for its magnetostrictive properties in applications such as sensors and actuators<ref>{{cite journal|last1=Olabi|title=Design and application of magnetostrictive materials|journal=Materials & Design|volume=29|issue=2|pages=469–483|date=2008|doi=10.1016/j.matdes.2006.12.016|url=http://doras.dcu.ie/15063/1/Olabi-MS-paper-12-09-06.pdf}}</ref> due to its high saturation magnetostriction (~200 ppm). CoFe<sub>2</sub>O<sub>4</sub> is not composed of rare-earth elements, making it a good substitute for Terfenol-D.<ref>{{cite journal|last1=Sato Turtelli|display-authors=etal|title=Co-ferrite – A material with interesting magnetic properties|journal=IOP Conference Series: Materials Science and Engineering|volume=60|article-number=012020|date=2014|issue=1 |doi=10.1088/1757-899X/60/1/012020|doi-access=free|bibcode=2014MS&E...60a2020T }}</ref> Moreover, its magnetostrictive properties can be tuned by inducing a magnetic uniaxial anisotropy.<ref>{{cite journal|last1=J. C. Slonczewski|title=Origin of Magnetic Anisotropy in Cobalt-Substituted Magnetite|journal=Physical Review|volume=110|issue=6|pages=1341–1348|date=1958|doi=10.1103/PhysRev.110.1341|bibcode=1958PhRv..110.1341S }}</ref> This can be done by magnetic annealing,<ref>{{cite journal|last1=Lo|title=Improvement of magnetomechanical properties of cobalt ferrite by magnetic annealing|journal=IEEE Transactions on Magnetics|volume=41|issue=10|pages=3676–3678|date=2005|doi=10.1109/TMAG.2005.854790|bibcode=2005ITM....41.3676L |s2cid=45873667}}</ref> magnetic field assisted compaction,<ref>{{cite journal|last1=Wang|title=Magnetostriction properties of oriented polycrystalline CoFe<sub>2</sub>O<sub>4</sub>|journal=Journal of Magnetism and Magnetic Materials|volume=401|pages=662–666|date=2015|doi=10.1016/j.jmmm.2015.10.073}}</ref> or reaction under uniaxial pressure.<ref>{{cite journal|last=Aubert|first=A.|date=2017|title=Uniaxial anisotropy and enhanced magnetostriction of CoFe<sub>2</sub>O<sub>4</sub> induced by reaction under uniaxial pressure with SPS|url=https://hal.archives-ouvertes.fr/hal-01636264|journal=Journal of the European Ceramic Society|volume=37 |issue=9|pages=3101–3105|doi=10.1016/j.jeurceramsoc.2017.03.036|arxiv=1803.09656|s2cid=118914808}}</ref> This last solution has the advantage of being ultrafast (20 min) due to the use of spark plasma sintering. The induced magnetic anisotropy in cobalt ferrite enhances the magnetoelectric effect in composite.<ref>{{cite journal|last1=Aubert|first1=A.|date=2017|title=Enhancement of the Magnetoelectric Effect in Multiferroic CoFe<sub>2</sub>O<sup>4</sup>/PZT Bilayer by Induced Uniaxial Magnetic Anisotropy|url=https://hal.archives-ouvertes.fr/hal-01636268|journal=IEEE Transactions on Magnetics|volume=53 |issue=11|pages=1–5|doi=10.1109/TMAG.2017.2696162|arxiv=1803.09677|bibcode=2017ITM....53A6162A |s2cid=25427820}}</ref>
It can be also used as electrocatalyst for the oxygen evolution reaction and as a material for fabricating electrodes for use in electrochemical capacitors (also named supercapacitors). These applications depend on redox reactions occurring at the ferrite surface. Cobalt ferrite can be prepared with controlled morphology and size to enhance the surface area, and thus the number of active sites.<ref name=Ortiz>{{cite journal |last1=Ortiz-Quiñonez |first1=Jose-Luis |last2=Das |first2=Sachindranath |last3=Pal |first3=Umapada |title=Catalytic and pseudocapacitive energy storage performance of metal (Co, Ni, Cu and Mn) ferrite nanostructures and nanocomposites |journal=Progress in Materials Science |date=October 2022 |volume=130 |article-number=100995 |doi=10.1016/j.pmatsci.2022.100995}}</ref>
One disadvantage of cobalt ferrite is its low electrical conductivity. Nanostructures of different shapes can be synthesized utilizing conducting substrates, such as reduced graphene oxide, to alleviate this disadvantage.<ref name="Ortiz" />
==References== {{Reflist}}
Category:Ceramic materials Category:Ferromagnetic materials Category:Ferrites Category:Cobalt(II) compounds Category:Iron(III) compounds
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