The Hall effect can be used to measure the strength of the magnetic field perpendicular to a current-carrying metal strip, called a Hall probe. The dimensions of the probe and the drift velocity for a given power-supply voltage are known. Ferromagnets Ferromagnetic materials are materials that have magnetic properties similar to those of iron. They can become permanently magnetized. Magnetic fields are produced by currents.
Permanent magnets are the result of magnetization currents flowing inside the material.
The magnetization currents in materials are a consequence of the electron's spin. Electrons have an internal property, called spin. Because they have spin, they have a magnetic moment, similar to a small current loop. Electrons by themselves act like tiny magnets. If you pick an axis, an electron's magnetic moment can either be parallel or anti-parallel to this axis.