MagnetoOptical

Magnetooptical refers to phenomena where magnetic ordering or magnetization influences optical properties such as polarization, reflectivity, or absorption. It encompasses effects observed when light interacts with magnetized materials or in nonreciprocal devices that rely on magnetic fields.

The most prominent effects are the Faraday effect and the magneto-optical Kerr effect. The Faraday effect is the rotation of the plane of polarization of linearly polarized light as it propagates through a magnetized medium, with the rotation angle proportional to the path length and the Verdet constant, and it is nonreciprocal. The magneto-optical Kerr effect concerns changes in the polarization and intensity of light reflected from a magnetized surface, enabling imaging and reading of magnetic domains.

Materials: magneto-optical effects are strongest in ferrimagnetic and ferromagnetic oxides and alloys, such as yttrium iron garnet (YIG), terbium-iron garnets, and bismuth-substituted iron garnets (Bi:YIG). The optical response arises from magnetization-induced off-diagonal components of the dielectric tensor, leading to polarization rotation or dichroism.

Applications: magneto-optical recording uses magneto-optical materials to write data with a laser and read with polarization analysis; MO disks and related media have been used; other uses include optical isolators and modulators in fiber-optic systems, magneto-optical sensors and imaging. The field also provides a tool for studying magnetic properties via magneto-optical spectroscopy.