Roadmap on nanoscale magnetic resonance imaging

Abstract

The field of nanoscale magnetic resonance imaging (NanoMRI) was started 30 years ago. It was motivated by the desire to image single molecules and molecular assemblies, such as proteins and virus particles, with near-atomic spatial resolution and on a length scale of 100 nm. Over the years, the NanoMRI field has also expanded to include the goal of useful high-resolution nuclear magnetic resonance (NMR) spectroscopy of molecules under ambient conditions, including samples up to the micron-scale. The realization of these goals requires the development of spin detection techniques that are many orders of magnitude more sensitive than conventional NMR and MRI, capable of detecting and controlling nanoscale ensembles of spins. Over the years, a number of different technical approaches to NanoMRI have emerged, each possessing a distinct set of capabilities for basic and applied areas of science. The goal of this roadmap article is to report the current state of the art in NanoMRI technologies, outline the areas where they are poised to have impact, identify the challenges that lie ahead, and propose methods to meet these challenges. This roadmap also shows how developments in NanoMRI techniques can lead to breakthroughs in emerging quantum science and technology applications.

2024 roadmap on magnetic microscopy techniques and their applications in materials science

“…MRFM has not remained the only approach to NanoMRI. Over the past decade, other types of magnetic sensors have emerged that allow for the detection and mapping of magnetic fields at the nanometre scale [228]. Most prominently, these include NMR sensors based on single NV centres in diamond, as well as the technique of ESR-STM, illustrated in figure 12 (see also sections 2 and 5).…”

“…It ranges from >100 nm for a nanomagnet employed in MRFM to <10 nm for the atomic-sized sensors associated with an NV centre or STM tip. It is therefore likely that the different techniques will find application for purposes that require either large imaging depth or optimal spatial resolution [228]. In addition, some techniques are compatible with room-temperature operation while others require cryogenic vacuum environment.…”

“…Furthermore, mechanical sensors are designed with the aim of minimising the damping coefficient γ = ω 0 m/Q where ω 0 , m, and Q are the sensor's angular resonance frequency, mass, and quality factor, respectively. There are two main strategies to achieve low γ: on the one hand, long and thin cantilevers or nanowires have low m and ω 0 [228]. On the other hand, strings or membranes made from e.g.…”

“…On the other hand, strings or membranes made from e.g. strained nitride have higher m and ω 0 but can possess enormously high Q [228,235]. NV-based NanoMRI, by contrast, is limited by optical shot noise as well as the spin coherence time; A microstrip serves as an antenna that generates radio-frequency pulses for NMR spin inversion [226].…”