Cryogenic scanning probe magnetometer

The electron spin of nitrogen-vacancy (NV) defects in diamond offer a promising platform for probing condensed matter systems by measuring the surface magnet field quantitatively with an operating temperature range from cryogenic temperature to above room temperature and a dynamic range spanning from DC to GHz. Here, we report our operation of cryogenic scanning nano magnetometer with single NV defect in diamond. To demonstrate the performance of our system, we measure the magnetic field on the surface of bulk Cu2OSeO3. With an NV defect about 10 nm from the sample surface, we directly measure the magnetic field component along the NV axis which shows a clear stripe structure with a period of 80 nm, attributed to the helical spin order. Thanks to the quantitative magnetic imaging, we reconstruct the vector field from the measurement result and obtain image of the helical magnetic field. The development of NV-based magnetic imaging will enable more previously inaccessible studies of physics of spins and currents in correlated electron materials and devices.