Magnetic resonance force microscopy

Magnetic resonance force microscopy has reached 90-nm resolution. MRFM maps the spins in a sample that is mounted on an ultrasensitive silicon cantilever hanging vertically over a sharp magnetic tip. If the tip’s magnetic field is highly inhomogeneous, an applied radio-frequency field will resonate with the spins in a highly localized region of the sample, and the cantilever will deflect due to the resulting forces. To achieve the nanoscale resolution, John Mamin, Dan Rugar, and their colleagues at the IBM Almaden Research Center in San Jose, California, made tips with magnetic gradients of more than a million teslas per meter and held the samples about 45 nm away. The test objects being imaged consisted of tiny islands of calcium fluoride evaporated onto the cantilever tip. The image shows a schematic (top), a simulation (middle), and the experimental result (bottom). Separations of 100 nm could be clearly resolved. Previously, the same...