MIT researchers came up with a new magnetic field detector that's 1,000 times more energy-efficient compared to the models that have come before it. This improvement now makes it possible for magnetometers to be downsized, resulting in miniature battery-powered devices for various applications, like material and medical imaging and contraband detection.

The U.S. Navy, for instance, is interested in throwaway magnetometers. Having these devices on hand will allow personnel to fly over certain parts of the ocean, for example, and simply scatter a handful of the magnetometers if measurements need to be taken. Improving magnetometer sensitivity and figuring out technology to bring down cost will be of great help for this particular application.

The magnetometers being discussed utilizes synthetic diamonds with nitrogen vacancies, or defects in the material that is highly sensitive to magnetic fields. A chip of diamond about the size of one-twentieth of a thumbnail can possess nitrogen vacancies in the trillions, each one capable of measuring magnetic fields.

Researchers had a problem before with combining all those measurements, taking into consideration the level of light a nitrogen vacancy emits when it is zapped with a laser. Magnetic fields can affect how much light is emitted because it can flip the spin or magnetic orientation of an electron. The stronger the magnetic field then, the more spins will be flipped, affecting the brightness of emitted light coming from nitrogen vacancies.

To address the issue with collecting measurements, Hannah Clevenson, an electrical engineering graduate student, and colleagues added a prism facet to one of the corners of a diamond, coupling the laser used to direct light to the surface of a chip into the side. When laser light is beamed towards the diamond chip, all light is absorbed and used, resulting in a more accurate measurement.

Researchers also calculated at which angle a laser beam should be poised so that once light enters the crystal it will stay confined, perpetually bouncing off the diamond's sides until all energy has been absorbed.

Thanks to the geometry that the nitrogen vacancies follow, re-emitted light come out at four angles, each one distinct. Putting a lens at the end of a diamond collects up to 20 percent of the re-emitted light. This should be enough to produce a reliable measurement using a light detector.

Frank Narducci with the U.S. Naval Air Systems Command said that nitrogen vacancies are nice to work with because there's very little needed to produce results. They don't have to be placed in a vacuum nor be cooled cryogenically and they just need a laser pointer for stimulation.