Magnetic bistability is determined by a material’s magnetic domain structure. A magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction.
Microwire metallic cores have a central axial magnetic domain surrounded by a radial domain (see figure, right). There are also closure domains at the ends of the microwire. This structure causes a bistable behavior — in other words, magnetization has only two states.
This magnetic bistability is not without limit; for example, it can be lost when the microwire length is shorter than the critical value determined by the diameter of its metal core and the size of its closure domain. This is why RVmagnetics works with its customers to design microwires for specific applications. Its MicroWire sensors are typically 1 to 4 centimeters in length.