Force-detected nuclear magnetic resonance: Recent advances and future challenges

TL;DR

This paper reviews recent progress in magnetic resonance force microscopy (MRFM) for detecting nuclear spins at nanoscale, highlighting advances, current limitations, and future challenges toward single-spin sensitivity and atomic-resolution molecular imaging.

Contribution

It summarizes recent experimental and theoretical developments in MRFM, emphasizing its improved sensitivity and potential for atomic-scale 3D imaging of molecules.

Findings

MRFM surpasses conventional NMR by eight orders of magnitude in sensitivity.

Recent techniques achieve 3D imaging with better than 10 nm resolution.

Challenges remain in reaching single nuclear spin detection and atomic resolution.

Abstract

We review recent efforts to detect small numbers of nuclear spins using magnetic resonance force microscopy. Magnetic resonance force microscopy (MRFM) is a scanning probe technique that relies on the mechanical measurement of the weak magnetic force between a microscopic magnet and the magnetic moments in a sample. Spurred by the recent progress in fabricating ultrasensitive force detectors, MRFM has rapidly improved its capability over the last decade. Today it boasts a spin sensitivity that surpasses conventional, inductive nuclear magnetic resonance detectors by about eight orders of magnitude. In this review we touch on the origins of this technique and focus on its recent application to nanoscale nuclear spin ensembles, in particular on the imaging of nanoscale objects with a three-dimensional (3D) spatial resolution better than 10 nm. We consider the experimental advances driving this work and highlight the underlying physical principles and limitations of the method. Finally, we discuss the challenges that must be met in order to advance the technique towards single nuclear spin sensitivity -- and perhaps -- to 3D microscopy of molecules with atomic resolution.