Nano Focus: Researchers take diamond defect to new depths in magnetic imaging
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itrogen-vacancy (NV) centers are a rising star in the field of highresolution magnetic imaging. Stable enough to capture condensed-matter phenomena at room temperature, these versatile, atom-sized defects are now soaring to new heights in the magnetism community—and descending to new depths. Research groups led by Ania Jayich from the University of California, Santa Barbara, and Patrick Maletinsky from the University of Basel in Switzerland, have independently developed NV-based sensors that can resolve nano-sized magnetic features at temperatures as low as a few degrees above zero Kelvin. With these sensors, condensed-matter physicists
now have access to a wider range of magnetic imaging temperatures. “There’s been a big push toward lowtemperature operations because there is a lot of very exciting electronic systems that exist at low temperatures,” says Maletinsky, assistant professor of experimental physics. “Graphene, quantum Hall effects, spin Hall effects—there’s a big variety.” For Maletinsky, who has been pushing the limits of NV-based imaging since his days as a postdoctoral researcher at Harvard University, his group’s most recent advance, published in Nature Nanotechnology (doi:10.1038/ NNANO.2016.63), represents an important technological breakthrough. NV centers are naturally occurring defects in diamond that consist of a substitutional nitrogen atom and a neighboring lattice vacancy. In the laboratory, NV centers are created by ion implanting nitrogen atoms in a piece of diamond,
Future gravitational-wave observatories could use different designs such as silicon test masses or cryogenically cooled optics. Larger interferometers would also increase signal-to-noise ratio for gravity waves; and future detectors could use different lasers, making way for materials with demonstrated optical properties at other wavelengths. LIGO’s next observation run is scheduled for this Fall, and will commence using the same mirrors and coatings as when LIGO made headlines earlier this year. This time, the two US-based interferometers will be joined by the Virgo interferometer in Pisa, Italy, for the first common datacollecting period with all three instruments operating at improved sensitivity levels. In the longer term, discussions about thermal noise center around mirrors with lower-loss coatings. Because interferometers detect the amplitude of a wave, a factor of two reduction in thermal noise would translate to a factor of eight in detection rate. Better understanding of coatings that will not jeopardize optical properties has great potential to improve LIGO sensitivity. “It helps to get the word out about the problem to the materials community,” Raab says.
Hard disk drive bit structure
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Nitrogen-vacancy (NV) magnetometry image of the bits of a hard disk at T = 6 K. Dark features correspond to the 5.3 G magnetic field contours (2892 MHz RF field). Scale bar, 100 nm. Credit: Nature Nanotechnology.
knocking carbon atoms out of place in the lattice. Each implanted nitrogen atom and associated vacancy together
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