The Degen Lab

Incomplete collection of nanoscale magnetic sensors, including experimental values for nanomechanical force sensors, Hall sensors, SQUID sensors and diamond single-spin sensors. The key to nanoscale spin detection is to combine small tip–sample separations (vertical axis) with good magnetic field sensitivity (horizontal axis), with the best magnetic moment sensitivity being in the bottom left region of this graph. Detecting the spin of a single electron requires a magnetic moment sensitivity of 1 Bohr magneton (μB; thick black diagonal line), whereas detecting the spin of a single proton requires an improvement of about 1,000 in sensitivity (dashed diagonal line). 1 Bohr magneton is roughly the magnetic dipole moment of an electron. 

See the original article in Nature Nanotechnology (link).