A spin exchange relaxation-free (SERF) magnetometer is a type of magnetometer developed at Princeton University in the early 2000s. SERF magnetometers measure magnetic fields by using lasers to detect the interaction between alkali metal atoms in a vapor and the magnetic field.
SERF components mockup
A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, one that measures the direction of an ambient magnetic field, in this case, the Earth's magnetic field. Other magnetometers measure the magnetic dipole moment of a magnetic material such as a ferromagnet, for example by recording the effect of this magnetic dipole on the induced current in a coil.
Helium vector magnetometer (HVM) of the Pioneer 10 and 11 spacecraft
The Magnetometer experiment for the Juno orbiter for Juno can be seen here on the end of a boom. The spacecraft uses two fluxgate magnetometers. (see also Magnetometer (Juno))
The compass is a simple type of magnetometer.
Coast and Geodetic Survey Magnetometer No. 18