CSU Physics Colloquium

Extraordinary Magnetoresistance Devices

Dr. Bruce A. Gurney

Hitachi Global Storage Technologies

Mon,  9/21

Magnetic field sensors utilizing the Extraordinary Magnetoresistance effect (EMR) have been proposed for application in future magnetic recording applications. EMR devices are metal semiconductor heterostructures comprised of a high mobility semiconductor in contact with a low resistance metallic shunt. A magnetic field applied perpendicular to the wafer plane changes electrical potentials within the device by selectively steering the current between the semiconductor and the shunt. Although this phenomenon is similar to the Hall Effect, modeling and experiments have shown that the sensitivity is larger than that of Hall sensors. Importantly, no ferromagnetic materials are incorporated in EMR, eliminating magnetic noise sources present in sensors with magnetic sense layers.

In this talk I will

• Describe the physics behind EMR,
• Show modeling results predicting magnetoresistance behavior,
• Compare those predictions with results from devices we have fabricated,
• Describe measurements of basic materials parameters and magnetoresistance behavior in simpler devices we have also fabricated
• Explore some of what we can learn from low temperature measurements.