The elastic deformation of the molecular structure of ferromagnetic materials like iron, nickel, cobalt and their alloys is called magnetostriction. The micromechanical deformation takes place during a change in the magnetisation. The magnetic structure of ferromagnetic materials consists of the sum of countless small elementary magnets. The elementary magnets with the same magnetic orientation are grouped in limited areas called Weiss domains. The magnetic orientation of the Weiss domains is arbitrary in the non-magnetised state. When exposed to an external magnetic field, a certain number of domains spontaneously