Mechanical Generation of Radio-Frequency Fields in Nuclear-Magnetic-Resonance Force Microscopy

Abstract

We present a method for magnetic-resonance force microscopy (MRFM) with ultralow dissipation, by using the higher modes of the mechanical detector as a radio-frequency (rf) source. This method allows MRFM on samples without the need to be close to a conventional electrically driven rf source. Furthermore, since conventional electrically driven rf sources require currents that give dissipation, our method enables nuclear-magnetic-resonance experiments at ultralow temperatures. Removing the need for an on-chip rf source is an important step towards an MRFM which can be widely used in condensed matter physics.

Magnetic Resonance Force Microscopy with a One-Dimensional Resolution of 0.9 Nanometers

“…One promising candidate for nano MRI is magnetic resonance force microscopy (MRFM). − The method employs an ultrasensitive nanomechanical transducer to detect the interaction between nuclear spins in the sample and a nanoscale magnetic tip by means of a magnetic force. Thanks to major advances in mechanical transduction − and magnetic gradient generation, − researchers have in recent years greatly improved the sensitivity of MRFM. Latest imaging experiments reported sensitivities on the order of 50–100 nuclear moments, corresponding to voxel sizes between (3.5 nm) 3 to (5.5 nm) 3 for statistically polarized protons in organic material. , In principle, MRFM even offers the sensitivity required to detect single proton magnetic moments but it is unclear at present whether this sensitivity can be extended to the context of three-dimensional MRI.…”

“…[1][2][3][4][5] The method employs an ultrasensitive nanomechanical transducer to detect the interaction between nuclear spins in the sample and a nanoscale magnetic tip by means of a magnetic force. Thanks to major advances in mechanical transduction [6][7][8][9][10][11] and magnetic gradient generation, 12,[12][13][14][15][16] researchers have in recent years greatly improved the sensitivity of MRFM.…”

Ultra-high-Q nanomechanical resonators for force sensing

“…With cantilevers in the kHz range, various protocols have been developed and tested [1,4,[98][99][100][101][102]. They typically rely on periodic spin inversions (induced by ac magnetic field pulses) to create a force acting on the cantilever.…”

Feasibility of imaging using Boltzmann polarization in nuclear Magnetic Resonance Force Microscopy

“…We apply this equation to show that we are able to measure the frequency shift of our resonator with a noise floor of 0.1 mHz. Furthermore, we demonstrate that we can use higher modes of the cantilever as the source of the alternating field in order to generate the required rf fields to saturate the magnetization of the spins with minimal dissipation 13 . These results suggest that imaging based on the Boltzmann polarization could be possible, allowing for the first MRFM imaging experiments performed at milliKelvin temperatures down to 10 mK and using the magnet-ontip geometry, as opposed to the sample-on-tip geometry more commonly found.…”

“…II C) of up to 0.3 mT. An alternative method to generate the required rf field is by using the higher modes of the cantilever, the proof of concept of which was recently demonstrated by Wagenaar et al 13 . Generating rf fields using the higher modes can be done with a small current in the rf wire to generate a magnetic drive field, or by using a piezo at the base of the cantilever, allowing experiments at larger distances from the rf wire, or even without one.…”