6: Review of Magnetostrictive (MSMs) and Giant Magnetostrictive Materials (GMSs)

Chapter 6 reviews magnetostriction as a property of ferromagnetic materials that causes them to change their shape when subjected to a magnetic field. The effect was first identified in 1842 by James Joule when observing a sample of nickel. This is known as the Joule effect. At a fundamental level, the change in dimensions results from the interactive coupling between an applied magnetic field and the magnetization and magnetic moments of the material's domains or magnetic dipoles. This chapter discusses the basic mechanisms of internal magnetic domains aligning in a magnetic field in magnetostrictive materials under no stress, as well as the same effect, but with the material initially under some stress. Magnetostriction causes mechanical deformation (length or volume change) in nearly all ferromagnetic materials when they are placed in a magnetic field. In the applied magnetic field (H) the domains move or rotate, so that the magnetic poles align, causing a dimensional change (d).