superparamagnetismn.
/ˌsuːpəparəˈmaɡnᵻtɪz(ə)m/, /ˌsjuːpəparəˈmaɡnᵻtɪz(ə)m/, U.S. /ˌsupərˌpɛrəˈmæɡnətɪz(ə)m/ Physics.
A phenomenon in which particles under a certain critical size and having a single magnetic domain can exhibit behaviour similar to paramagnetism despite being below the Curie temperature (for a ferromagnetic substance) or the Néel temperature (for an antiferromagnetic or ferrimagnetic substance).The phenomenon arises when the energy required to change the direction of a particle's magnetic moment is comparable to its thermal energy.
ΚΠ
1956 C. P. Bean & J. D. Livingston in Jrnl. Appl. Physics 27 1448 (title) Magnetic granulometry and super-paramagnetism.
1970 Science 21 Aug. 698/3 The lower susceptibility after heating may be ascribed..to growth of particles (by coalescence) above the critical size for superparamagnetism.
1991 Corrosion Sci. 32 167 All rust samples exhibit superparamagnetism due to fine particles.
2010 N. A. Spaldin Magn. Materials (ed. 2) xii. 150 Superparamagnetism can be destroyed by reducing the temperature, increasing the particle size, or increasing the anisotropy.
This is a new entry (OED Third Edition, June 2012; most recently modified version published online March 2022).
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n.1956