# Cobalt ferrite
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{{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 = [{{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}}]
| 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}}
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'''Cobalt ferrite''' is a semi-hard [ferrite](/source/Ferrite_(magnet)) with the [chemical formula](/source/chemical_formula) CoFe2O4 (CoO·Fe2O3). The substance can be considered as between a soft and hard magnetic material and is usually classified as a semi-hard material.[{{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}}]
== Uses ==
Cobalt ferrite is mainly used for its [magnetostrictive](/source/magnetostrictive) properties in applications such as sensors and actuators[{{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}}] due to its high saturation magnetostriction (~200 ppm). CoFe2O4 is not composed of [rare-earth elements](/source/rare-earth_elements), making it a good substitute for [Terfenol-D](/source/Terfenol-D).[{{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 }}] Moreover, its magnetostrictive properties can be tuned by inducing a magnetic uniaxial [anisotropy](/source/anisotropy).[{{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 }}] This can be done by magnetic [annealing](/source/Annealing_(materials_science)),[{{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}}] magnetic field assisted compaction,[{{cite journal|last1=Wang|title=Magnetostriction properties of oriented polycrystalline CoFe2O4|journal=Journal of Magnetism and Magnetic Materials|volume=401|pages=662–666|date=2015|doi=10.1016/j.jmmm.2015.10.073}}] or reaction under uniaxial pressure.[{{cite journal|last=Aubert|first=A.|date=2017|title=Uniaxial anisotropy and enhanced magnetostriction of CoFe2O4 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}}] This last solution has the advantage of being ultrafast (20 min) due to the use of [spark plasma sintering](/source/spark_plasma_sintering). The induced magnetic anisotropy in cobalt ferrite enhances the [magnetoelectric effect](/source/magnetoelectric_effect) in composite.[{{cite journal|last1=Aubert|first1=A.|date=2017|title=Enhancement of the Magnetoelectric Effect in Multiferroic CoFe2O4/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}}]
It can be also used as [electrocatalyst](/source/electrocatalyst) for the [oxygen evolution reaction](/source/oxygen_evolution_reaction) and as a material for fabricating electrodes for use in electrochemical capacitors (also named [supercapacitors](/source/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.[{{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}}]
One disadvantage of cobalt ferrite is its low electrical conductivity. [Nanostructures](/source/Nanostructures) of different shapes can be synthesized utilizing conducting substrates, such as reduced graphene oxide, to alleviate this disadvantage.