The Giant MagnetoResistance (GMR) effect is a magnetic coupling mechanism that can be obtained in multilayer structures of few nanometers thick. In these devices, and at room temperature, the resistance is a function of the external magnetic field, at optimal levels for being used as sensors. Since the GMR effect was reported, scientists and engineers have dedicated their effort to this topic. This way, after two decades, a a very good knowledge of the GMR underlying physics together with notable designs of GMR based devices are nowadays available. They were initially used in the read heads of hard drives, but the constant evolution that this technology has experienced has open new fields of application, mainly related to the measurement of small magnetic fields using miniaturized devices, such as biotechnology and microelectronics.
Regarding the microelectronics case, these sensors can be potentially used in those scenarios that require a detection or measurement of nonintrusive power by the indirect measurement of the magnetic field.
In this chapter, an overview to the current research regarding the application of GMR sensors in the measurement of electrical currents at the integrated circuit (IC) level is drawn. In this particular case is important to take account of particular parameters of the GMR devices such as the sensing structures, the geometric arrangement and implementation of the sensors, the considered linear range, undesired couplings, biasing, hysteresis, temperature drifts, ... We have also described some cases of success describin particular applications of these devices. Finally, some aspects related to the monolithic integration of GMR devices onto standard CMOS engineered chips are also considered in this chapter.