Micro-magnetometer Nanowerk News) MIT researchers have developed a new, ultrasensitive magnetic-field detector that is 1,000 times more energy-efficient than its predecessors. It could lead to miniaturized, battery-powered devices for medical and materials imaging, contraband detection, and even geological exploration.

Magnetic-field detectors, or magnetometers, are already used for all those applications. But existing technologies have drawbacks: Some rely on gas-filled chambers; others work only in narrow frequency bands, limiting their utility.

Synthetic diamonds with nitrogen vacancies (NVs) � defects that are extremely sensitive to magnetic fields � have long held promise as the basis for efficient, portable magnetometers. A diamond chip about one-twentieth the size of a thumbnail could contain trillions of nitrogen vacancies, each capable of performing its own magnetic-field measurement.

The problem has been aggregating all those measurements. Probing a nitrogen vacancy requires zapping it with laser light, which it absorbs and re-emits. The intensity of the emitted light carries information about the vacancy magnetic state.

�In the past, only a small fraction of the pump light was used to excite a small fraction of the NVs,� says Dirk Englund, the Jamieson Career Development Assistant Professor in Electrical Engineering and Computer Science and one of the designers of the new device. �We make use of almost all the pump light to measure almost all of the NVs.�

The MIT researchers report their new device in the latest issue of Nature Physics ("roadband Magnetometry and Temperature Sensing with a Light Trapping Diamond Waveguide"). First author on the paper is Hannah Clevenson, a graduate student in electrical engineering who is advised by senior authors Englund and Danielle Braje, a physicist at MIT Lincoln Laboratory. They�re joined by Englund students Matthew Trusheim and Carson Teale (who also at Lincoln Lab) and by Tim Schröder, a postdoc in MIT Research Laboratory of Electronics.