Magnetizing

Magnetizing is the process of imparting magnetic properties to a material by aligning its magnetic moments, typically in ferromagnetic or ferrimagnetic substances. In scientific terms, magnetization is the net magnetic moment per unit volume of a material, while magnetizing refers to the act of inducing that state, often by exposing the material to an external magnetic field.

In ferromagnetic materials, many microscopic regions called magnetic domains are magnetized in random directions when the material is unmagnetized. Applying an external magnetic field causes domain walls to move and domains aligned with the field to grow, increasing the overall magnetization. With sufficient field strength, the material approaches magnetic saturation, after which additional field increases have little effect. The behavior depends on temperature; above the Curie temperature, ferromagnetic order is lost and magnetization disappears.

Methods of magnetizing include stroking with a strong magnet, passing an electric current through a coil around the material (creating an electromagnet), or exposing the material to a strong, rapidly changing magnetic field. Thermal treatment near or above the Curie temperature can erase existing magnetization, while mechanical shocks and demagnetizing fields can gradually reduce it.

Permanent magnets and soft magnets illustrate different outcomes of magnetization. Materials with high coercivity retain magnetization as remanent magnetization after the external field is removed; soft magnetic materials exhibit low coercivity and readily demagnetize. Common magnetized materials include iron and its alloys, nickel, cobalt, and specialized permanent-magnet alloys such as neodymium-iron-boron and samarium-cobalt.

Applications span from permanent magnets in motors and sensors to electromagnets in lifting devices and circuitry.