33 - Magnetostriction effects in ferrites

Abstract

Magnetostriction is a phenomenon common to all magnetic materials that changes their state of magnetization that can occur when the external magnetic field change or other factors such as temperature, torsion, or stress vary. In many fields, especially in industry and medicine, this phenomenon can have a wide range of applications in what is generically called the field of sensors and actuators. The magnetostriction of substances is characterized by volume or linear magnetostriction coefficients and by their variation with the applied magnetic field known as strain derivative. For a long time, the researchers’ attention was polarized by metal alloys with high magnetostriction coefficients fabrication and by limiting the values of these coefficients in the case of ferrites used in electronics. The discovery of the conditions under which cobalt ferrite and compositions are based may have significant values of magnetostrictive coefficients which has shifted researchers’ interest in this field because the applications of sensors and actuators have created an extensive market for easy-to-manufacture and inexpensive sensors and actuators. The ferrites are returned into attention, and the methods of synthesis, granular and intergranular structure, distribution of cations in the crystal lattice, doping influence on magnetization, coercive field, and magnetostriction coefficients are studied for obtaining comparable performance with other materials suitable for the same type of applications. This chapter briefly presents the fundamentals of the phenomenon, the measuring methods of magnetostriction coefficients in bulk and thin film samples, and resumes the results of various research groups that strive to limit costs and increase the performance of ferrites used in miniaturized sensors and actuators.