magnetostriktiö

Magnetostriction is a property of ferromagnetic materials that causes them to change shape or dimensions when exposed to a magnetic field. This change in shape is reversible, meaning the material will return to its original size and shape when the magnetic field is removed. The phenomenon is also known as the Joule effect, named after James Prescott Joule who first observed it in 1842.

The underlying mechanism of magnetostriction involves changes in the magnetic domains within the material. Magnetic domains are small regions where the magnetic moments of atoms are aligned. When an external magnetic field is applied, these domains reorient themselves to align with the field. This reorientation process leads to changes in the distances between atoms, resulting in the macroscopic expansion or contraction of the material. The magnitude of the magnetostrictive effect varies significantly between different materials.

Conversely, the inverse magnetostrictive effect, known as the Villari effect, occurs when a material undergoes mechanical stress and its magnetization changes. This relationship between mechanical stress and magnetization is fundamental to many applications.

Magnetostrictive materials are utilized in a variety of technologies. They are commonly found in actuators, where their ability to change shape precisely under magnetic control allows for fine movements in devices. They are also used in sensors, such as pressure sensors and strain gauges, where the change in magnetization due to applied stress can be measured. Furthermore, magnetostrictive materials are employed in sonar transducers, ultrasonic generators, and high-frequency resonant devices due to their efficient conversion of magnetic energy into mechanical vibration and vice versa.