The Giant Magnetoimpedance (GMI) effect refers to the strong and sensitive change of impedance of a magnetic conductor with a small variation in the DC magnetic field.
Even though an RVmagnetics MicroWire sensor is a magnetized element, its permeability is ~ 1, like in a vacuum. This enables the sensor to operate in heavily magnetized environments, to provide measurements on the magnetic field , and at the same time to not have biased measurements from the effects of the heavy magnetic environment. Although MicroWire is a magnetic sensor it does not work with GMI effect, it works with audio frequencies.