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Nanomagnetism at NIST: Magnetic sensors
The Giant Magnetoresistance (GMR) and the Anisotropic Magnetoresistance (AMR) effects make electrical detection of magnetic fields easy and inexpensive and have led to a large number of applications of magnetic sensors based on this effect. The most high profile application is the read head in a hard disk drive. Additional applications range from detecting biological pathogens to homeland security applications. Combining a movable hard magnet with a magnetoresistive sensor leads to a variety of other applications where one would not normally imagine a magnetic field playing a role, such as a position sensor.
NIST has an interlaboratory project to develop high sensitivity low field magnetic sensors based on ultrathin magnetic films. The work involves optimizing materials and processing conditions to find materials with large susceptibilities and a large magnetoresistance, measuring the domain patterns to understand the defects that reduce the susceptibility and increase the noise, fabricating device structures that incorporate optimized materials into sensors, measuring the noise properties, and modeling the devices.
Related work in developing sensors for data recovery has led to a number of high profile applications including an attempt to recover the information from a famous erased tape.