High-efficiency resonant amplification of weak magnetic fields for single spin magnetometry at room temperature

Abstract

Magnetic resonance techniques not only provide powerful imaging tools that have revolutionized medicine, but they have a wide spectrum of applications in other fields of science like biology, chemistry, neuroscience, and physics. However, current state-of-the-art magnetometers are unable to detect a single nuclear spin unless the tip-to-sample separation is made suffciently small. Here,we demonstrate theoretically that by placing a ferromagnetic particle between a nitrogen-vacancy (NV) magnetometer and a target spin, the magnetometer sensitivity is improved dramatically. Using materials and techniques already experimentally available, our proposed setup is sensitive enough to detect a single nuclear spin within ten milliseconds of data acquisition at room temperature. The sensitivity is practically unchanged when the ferromagnet surface to the target spin separation is smaller than the ferromagnet lateral dimensions; typically about a tenth of a micron. This scheme further benefits when used for NV ensemble measurements, enhancing sensitivity by an additional three orders of magnitude. Our proposal opens the door for nanoscale nuclear magnetic resonance (NMR) on biological material under ambient conditions.