Abstract

Magnetic resonance imaging (MRI) is a powerful imaging technique that typically operates on the scale of millimetres to micrometres. Conventional MRI is based on the manipulation of nuclear spins with radio-frequency fields, and the subsequent detection of spins with induction-based techniques. An alternative approach, magnetic resonance force microscopy (MRFM), uses force detection to overcome the sensitivity limitations of conventional MRI. Here, we show that the two-dimensional imaging of nuclear spins can be extended to a spatial resolution better than 100|[nbsp]|nm using MRFM. The imaging of 19F nuclei in a patterned CaF2 test object was enabled by a detection sensitivity of roughly 1,200 nuclear spins at a temperature of 600|[nbsp]|mK. To achieve this sensitivity, we developed high-moment magnetic tips that produced field gradients up to 1.4|[nbsp]||[times]||[nbsp]|106|[nbsp]|T|[nbsp]|m|[minus]|1, and implemented a measurement protocol based on force-gradient detection of naturally occurring spin fluctuations. The resulting detection volume was less than 650|[nbsp]|zeptolitres. This is 60,000 times smaller than the previous smallest volume for nuclear magnetic resonance microscopy, and demonstrates the feasibility of pushing MRI into the nanoscale regime.