Definition
The gradual loss of magnetic strength in a permanent magnet caused by the magnet's own internal magnetic field acting against itself. The magnetic domains inside the material slowly drift out of alignment over time, weakening the magnet without any outside influence.
Plain English
A magnet quietly loses some of its strength on its own, just because of how its internal magnetic field works against itself. Nothing has to hit it, heat it, or interfere with it -- it weakens over time naturally.
Context Anchor
Seen in aircraft maintenance discussions involving permanent magnets, such as magnets used in ignition or compass-related equipment.
Derivation
"Self" means the action comes from within the object itself. "Demagnetization" combines "de-" (to remove or reverse) with "magnetization" (the state of being magnetic). Together: the magnet weakens itself, with no external cause.
Why Pilots Care
Components like magnetos and compasses depend on strong, stable permanent magnets. As self-demagnetization slowly reduces magnet strength over years of service, performance can drift -- weaker spark output from a magneto, or a less responsive compass. This is one reason these components are inspected, tested, and eventually overhauled or replaced.
Grounding Statement
Picture a small permanent magnet in an aircraft component becoming weaker over time even though nobody intentionally erased its magnetism.
Intuition Check
Self-demagnetization does not mean a mechanic deliberately removed the magnetism. It means the magnet’s own field helped reduce its strength.
Example Sentence 1
The mechanic explained that the old magneto's weak spark was partly due to self-demagnetization of its permanent magnet over decades of service.
Example Sentence 2
Self-demagnetization over time can reduce the holding power of a permanent magnet used in aircraft instruments.