Magnetic resonance force microscopy

The MRFM concept combines the ideas of magnetic resonance imaging (MRI) and atomic force microscopy (AFM).

Conventional MRI employs an inductive coil as an antenna to sense resonant nuclear or electronic spins in a magnetic field gradient.

As the ferromagnetic tip moves close to the sample, the atoms' nuclear spins become attracted to it and generate a small force on the cantilever.

Because the signal-to-noise ratio is inversely proportional to the sample size, Brownian motion is the primary source of noise at the scale in which MRFM is useful.

[4] In 2009 researchers at IBM and Stanford announced that they had achieved resolution of better than 10 nanometers, imaging tobacco mosaic virus particles on a nanometer-thick layer of adsorbed hydrocarbons.