Superferromagnetism is the

magnetism Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...

of an ensemble of magnetically interacting super-moment-bearing material particles that would be

superparamagnetic Superparamagnetism is a form of magnetism which appears in small ferromagnetic or ferrimagnetic nanoparticles. In sufficiently small nanoparticles, magnetization can randomly flip direction under the influence of temperature. The typical time be ...

if they were not interacting.

Nanoparticles A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 1 ...

of iron oxides, such as

ferrihydrite Ferrihydrite (Fh) is a widespread hydrous ferric oxyhydroxide mineral at the Earth's surface, and a likely constituent in extraterrestrial materials. It forms in several types of environments, from freshwater to marine systems, aquifers to hydro ...

(nominally FeOOH), often cluster and interact magnetically. These interactions change the magnetic behaviours of the nanoparticles (both above and below their blocking temperatures) and lead to an ordered low-temperature phase with non-randomly oriented particle super-moments.

Discovery

The phenomenon appears to have been first described and the term "superferromagnatism" introduced by Bostanjoglo and Röhkel, for a metallic film system. A decade later, the same phenomenon was rediscovered and described to occur in small-particle systems. The discovery is attributed as such in the scientific literature.

References

Magnetic ordering {{Physics-stub