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Magnetostriction is a property of ferromagnetic materials that causes them to change shape or dimensions when subjected to a magnetic field. This phenomenon is also known as the Joule effect. Conversely, when a magnetostrictive material is subjected to mechanical stress, its magnetization changes, a phenomenon known as the Villari effect or inverse magnetostriction.

The effect arises from changes in the magnetic domain structure of the material. In a magnetic field, the magnetic domains tend to align with the field, and this alignment is accompanied by a change in the material's shape. The magnitude and sign of the magnetostriction depend on the specific material. Some materials, like iron, expand in a magnetic field, while others, like nickel, contract. Rare-earth elements, particularly terbium and dysprosium, exhibit very large magnetostriction effects.

Magnetostriction is utilized in various technologies. For instance, it's the operating principle behind magnetostrictive transducers, which convert electrical energy into mechanical vibrations or vice versa. These transducers are used in applications such as ultrasonic cleaning, sonar systems, and actuators. The inverse magnetostriction effect is employed in magnetic sensors to detect mechanical stress or pressure. Materials exhibiting significant magnetostriction are crucial components in many modern electronic and electromechanical devices. The development of new magnetostrictive materials with enhanced properties continues to be an area of active research.