What does demagnetisation mean?
Demagnetisation refers to the process by which an object loses its magnetic properties, either through deliberate intervention or natural decay. It occurs when the alignment of magnetic domains within a material — typically ferromagnetic substances like iron — is disrupted, causing them to return to a random orientation with no net magnetic field. The process can be achieved in several ways: applying an alternating magnetic field that gradually diminishes in strength (the principle behind degaussing coils), heating the material above its Curie point, subjecting it to mechanical shock, or simply allowing it to weaken over time. Demagnetisation has significant practical importance: it protects ships from magnetic mines, erases sensitive data from magnetic storage media, prevents tools from interfering with precision instruments, and enables accurate geological dating through the study of ancient magnetic records preserved in rocks.
nounThe process of removing or reducing the magnetic properties of an object, or the loss of magnetisation from a material.
- The removal or reduction of magnetic properties from an object or material, whether deliberate (e.g. erasing data, neutralising tools) or natural (loss of magnetism over time).
"Regular demagnetisation of the ship's hull protected it against magnetic mines."
"The technician performed a full demagnetisation of the CRT monitor to eliminate colour distortion."
"Over centuries of exposure to heat, the rock samples underwent partial demagnetisation, erasing their original magnetic record."
Rarely used in plural form; the word typically functions as an uncountable mass noun referring to the process itself. Plural use appears mainly in technical texts referring to multiple distinct instances or events.
"Repeated demagnetisations of the sample gradually erased all residual magnetisation."
During WWII, Allied ships were 'wiped' of magnetism — a process called degaussing — so German magnetic mines couldn't detect and detonate beneath them.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of demagnetisation
The word derives from 'magnet', which traces back through Latin 'magnet-' (from Greek 'Magnēs lithos', meaning 'stone of Magnesia' — a region of Thessaly where lodestone was found) combined with the prefix 'de-' indicating reversal or removal, and the suffix '-isation' denoting a process. The verb 'demagnetise' emerged in the 19th century alongside growing scientific understanding of electromagnetism, with the noun form following naturally. Cognates sharing the same root include 'magnetic', 'magnetism', and 'magnesia'.
Related word forms
How demagnetisation is actually used
Formal/technical register, common in physics, engineering, and electronics contexts. British spelling uses -isation; American spelling is demagnetization. In computing contexts, 'degaussing' is more frequently used for the same operation.
Easily confused with demagnetisation
Degaussing is essentially the same process, but the term is typically used for electronic devices and data storage, while demagnetisation is the broader physical term.