Definition
A material, such as iron, nickel, cobalt, or certain alloys, that is strongly attracted to a magnet and can itself be magnetized. Ferromagnetic materials concentrate magnetic field lines and retain magnetism after the magnetizing force is removed.
Plain English
A material that a magnet pulls on strongly and that can be turned into a magnet itself. Iron is the classic example.
Context Anchor
Seen in discussions of magnetic compasses, aircraft structures, tools, and equipment that may affect magnetic instruments.
Derivation
From the Latin ferrum meaning iron, plus magnetic. The term literally means iron-like in magnetic behavior, since iron is the most familiar material that responds strongly to magnets.
Why Pilots Care
Ferromagnetic materials near the compass can produce deviation errors that must be identified and compensated for accurate heading information.
Analogy
A magnet sticking firmly to a steel tool is a simple example of ferromagnetic behavior.
Intuition Check
Ferromagnetic does not mean any metal. Aluminum and copper are metals, but they are not ferromagnetic in normal aviation use; iron and many steels are.
Example Sentence 1
The compass case is built from non-ferromagnetic material so it does not interfere with the magnetic needle inside.
Example Sentence 2
During the compass swing, the technician noted that certain avionics mounts contained ferromagnetic material and adjusted the deviation card accordingly.