Magnetostriction

Property of materials that causes them to change their shape during magnetization

Magnetostriction is a property of magnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of materials' magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ. The effect was first identified in 1842 by James Joule when observing a sample of iron.

This keyword could refer to multiple things. Here are some suggestions: