In our life, the magnetic £eld is omnipresent. It is a £eld generated by Earth superimposed on £eld coming from outer space combined with magnetic pollution. Presence of this £eld causes also that magnetic materials act as a secondary magnetic £eld source due to the demagnetizing £eld. This £eld known as magnetic signature is often used for detection of magnetic objects, for example, sea ships. Moreover, magnetic history of the formation of the Earth’s crust is available in rocks and stones and disciplines studying such effects are known as paleomagnetism and archeomagnetism.