GMR Sensors: Technologies and Medical Applications

Giant Magnetoresistance (GMR) is a quantum mechanical effect found in thin film materials that are composed of alternating nano-size ferromagnetic and non magnetic layers. When a GMR material is in the presence of a magnetic field a change in electrical resistance is observed. The GMR effect has been used to produce magnetic sensors that can be used in a variety of applications. Although there are some sensors that have greater sensitivity and lower magnetic detection limits, GMR sensors have more commercial potential due to their small size, low power use, low fabrication cost, and their reproducible operation in very narrow magnetic ranges. The medical field is rapidly adopting the use of GMR magnetic sensors for many medical applications; this is leading to an increase in the number of patents that include GMR sensors. Two of the most promising medical application areas for GMR sensors are medical diagnostics and implant communication. This article reviews the GMR mechanism, measurement, fabrication techniques, and discusses a variety of medical applications and patents that incorporate GMR sensors.