Magnetostriction and Terfenol-D

In this talk, which is tutorial in nature, I present a review of the phenomenon of magnetostriction in magnetic materials. Magnetostriction has its origin in the spin-orbit coupling of the electrons responsible for the magnetization. Terfenol-D (Dy0.73Tb0.27Fe1.95) has such an enormous magnetostriction parameter that it has acquired "smart material" status. Suitably oriented crystals have strain changes of approximate to 0.2% when the magnetization direction is rotated by 90 degrees. Devices based on this material include microphones, inch-worm motors, actuators, etc. On a fundamental level, magnetostriction provides an interaction mechanism between photons and phonons. Calculations and experimental data for 17 GHz microwave reflection and transmission measurements are presented. Finally, possible experiments at optical frequencies are suggested.