Diamond definition

Nitrogen defects in diamond are showing their potential for very-high-resolution magnetic sensing

Credit: © 2008 NPG

Magnetometers with resolution down to the nanometre scale would be able to detect the magnetic field of a single electron or nucleus. Such technology could be used to image complex biological molecules, or to read encoded bits of information in quantum computing. This week, two collaborations of scientists^1,2,3 show how it can be done using diamonds with defects called nitrogen vacancies.

Nitrogen vacancies are naturally occurring areas of diamond crystals where a carbon atom has been replaced by nitrogen, leaving a stray electron. They account for the pink colour of some diamonds, and their potential for sensing tiny magnetic fields is being realized.

One group of scientists, led by Mikhail Lukin of Harvard University^1,2, used microwaves to manipulate the electron spin states of nitrogen vacancies in bulk diamond, and managed to detect a magnetic field of just 3 nanoteslas. Another group led by Fedor Jelezko of Stuttgart University³ attached a diamond nanocrystal, containing a single nitrogen vacancy, to the tip of an atomic force microscope. This allowed the researchers to build up a detailed magnetic image of a nickel nanoparticle.

The resolution of magnetic resonance imaging is limited only by its sensitivity to magnetic fields. Therefore combinations of the ultrasensitive magnetic imaging techniques from these two groups could lead to impressive new magnetic sensors, with the ultimate goal of resolving individual nuclear spins in a molecule.