Superferromagnetism is the magnetism of an ensemble of magnetically interacting super-moment-bearing material particles that would be superparamagnetic if they were not interacting. Nanoparticles of iron oxides, such as ferrihydrite (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.
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.
- D.G. Rancourt. "Magnetism of Earth, planetary, and environmental nanoparticles" In: Nanoparticles and the Environment, J.F. Banfield and A. Navrotsky (editors), Reviews in Mineralogy and Geochemistry 44 (2001) 217-292 (Chapter 7).
- O. Bostanjoglo andK. Röhkel, "Superferromagnetism in gadolinium films", Physica Status Solidi A, Volume 11, Issue 1, pages 161-166, 16 May 1972.
- S. Mørup , M. B. Madsen , J. Franck , J. Villadsen , and C. J. W. Koch, "A new interpretation of Mössbauer spectra of microcrystalline goethite: "super-ferromagnetism" or "super-spin-glass" behavior?" J. Magn. Magn. Mater. 40, 163 (1983).
- D. G. Rancourt and J. M. Daniels, "The Influence of Unequal Magnetization Direction Probabilities on Mössbauer Spectra of Superparamagnetic Particles" Phys. Rev. B 29, 2410 (1984).
- S. Bedanta et al., "Superferromagnetism in dipolarly coupled L10 FePt nanodots with perpendicular magnetization", Applied Physics Letters, 107, 152410 (2015).