Definition
Materials that are strongly attracted to magnets and can themselves be magnetized. The main ferromagnetic metals are iron, nickel, cobalt, and many of their alloys, including most steels. Because they hold and conduct magnetic fields well, they are the materials used for magnetic particle inspection and for parts that must work with magnets or magnetic fields.
Plain English
Metals that magnets stick to, and that can be turned into magnets themselves. Iron and steel are the most common examples.
Context Anchor
Seen in aircraft maintenance when dealing with magnetic compasses, steel parts, electrical components, and inspection methods that use magnetism.
Derivation
From the Latin ferrum, meaning iron, plus magnetic. So ferromagnetic literally means iron-like in its magnetic behavior. This makes sense because iron is the classic example of a metal that magnets pull on strongly.
Why Pilots Care
Uncontrolled ferromagnetic materials near a magnetic compass cause deviation errors that affect heading accuracy and navigation safety.
Analogy
A steel paper clip is a simple example: a magnet pulls it strongly, and after contact with a magnet it may briefly pick up other small steel objects.
Intuition Check
Do not assume all metals are ferromagnetic. Aluminum is a metal commonly used in aircraft, but a magnet does not pull on it strongly.
Example Sentence 1
Magnetic particle inspection can only be used on ferromagnetic materials, so the aluminum landing gear strut must be checked using a different method.
Example Sentence 2
The mechanic checked the area around the magnetometer for ferromagnetic materials before performing the compass swing.