Magnetometers are miniature electro-mechanical devices that measure the magnetic field they are placed in.
Soft-iron materials are ones which are not magnetic themselves, but generate a magnetic field.
- Ferrous EMI shielding
- Battery contacts
Hard-iron materials are ones which are naturally magnetic.
- Proximity switches
- Hall-effect sensors
Magnetometers are not directly affected by electromagnetic waves. However, if these waves pass through conductive substances (including those inside the magnetometer itself), these can induce a current which inturn creates a magnetic field.