Magnetoelectric effect

In its most general form, the magnetoelectric effect (ME) denotes any coupling between the magnetic and the electric properties of a material. The first example of such an effect was described by Wilhelm Röntgen in 1888, who found that a dielectric material moving through an electric field would become magnetized. A material where such a coupling is intrinsically present is called a magnetoelectric. Historically, the first and most studied example of this effect is the linear magnetoelectric effect. Mathematically, while the electric susceptibility and magnetic susceptibility describe the electric and magnetic polarization responses to an electric, resp. a magnetic field, there is also the possibility of a magnetoelectric susceptibility which describes a linear response of the electric polarization to a magnetic field, and vice versa: The tensor must be the same in both equations. Here, P is the electric polarization, M the magnetization, E and H the electric and magnetic fields. The SI Unit of is (seconds per meter) which can be converted to the practical unit by: For the CGS unit (assuming rationalized Gaussian units): where is the speed of light in vacuum. The first material where an intrinsic linear magnetoelectric effect was predicted theoretically and confirmed experimentally is Cr2O3. This is a single-phase material. Multiferroics are another example of single-phase materials that can exhibit a general magnetoelectric effect if their magnetic and electric orders are coupled. Composite materials are another way to realize magnetoelectrics. There, the idea is to combine, say a magnetostrictive and a piezoelectric material. These two materials interact by strain, leading to a coupling between magnetic and electric properties of the compound material. Some promising applications of the ME effect are sensitive detection of magnetic fields, advanced logic devices and tunable microwave filters. The first example of a magnetoelectric effect was discussed in 1888 by Wilhelm Röntgen, who showed that a dielectric material moving through an electric field would become magnetized.