Koercitiivisyyteen

Koercitiivisyyteen, often translated as coercivity, is a fundamental property of ferromagnetic materials that describes their resistance to becoming demagnetized. It quantifies the strength of the magnetic field that must be applied in the opposite direction to reduce the magnetization of a material to zero after it has been saturated. Materials with high coercivity are considered hard magnetic materials and are difficult to magnetize and demagnetize. Conversely, materials with low coercivity are soft magnetic materials and are easily magnetized and demagnetized.

The phenomenon of coercivity is closely related to the magnetic domain structure within a material. Magnetic domains are regions where the magnetic moments of atoms are aligned. When an external magnetic field is applied, these domains can grow, shrink, or rotate. Coercivity is influenced by factors such as the presence of impurities, crystal defects, grain boundaries, and the shape of the material. These imperfections can impede the movement of domain walls, thus increasing the resistance to demagnetization.

Hard magnetic materials, characterized by high coercivity, are used in applications requiring permanent magnets, such as electric motors, loudspeakers, and data storage devices like hard disk drives. Soft magnetic materials, with low coercivity, are employed in applications where magnetic flux needs to change rapidly and easily, such as in transformers, inductors, and magnetic shielding. The specific value of coercivity is a critical parameter in selecting the appropriate magnetic material for a given technological application.