A Magnetic Dependent Resistor (MDR) is a magnetosensitive component whose resistance value depends on the magnetic flux that passes through it. The effect is called the Gaussian effect and occurs when a current-carrying conductor penetrates vertically into a magnetic field.
In the Gauss effect, the magnetic field attempts to deflect the charge carriers from their path through the conductor. The current path through the conductor narrows, causing the conductive cross-section to decrease and the electrical resistance to increase. The Gaussian effect occurs to varying degrees in all materials.
Therefore, materials in which the Gaussian effect is particularly pronounced are used in MDRs, known as field plates. Indium antimonide (InSb) with nickel antimonide (NiSb) are such materials that exhibit a pronounced Gaussian effect as semiconductors. Theindium layer contains nickel antimonide as the conductive material, which deflects the current under the influence of a magnetic field and thus lengthens the path through the semiconductor material. If the magnetic flux density (B) increases, the resistance value thus increases. The resistance values of field plates can range from a few ohms to several kilo-ohms.
Field plates are used in Gauss and magnetometers.