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O: Fachverband Oberflächenphysik
O 105: Scanning Probe Techniques II: Method Development (joint session O/CPP)
O 105.6: Vortrag
Donnerstag, 19. März 2020, 11:45–12:00, WIL C107
Sensing with an ultra-sensitive cantilever — •Marc-Dominik Krass, Urs Grob, Raphael Pachlatko, Alexander Eichler, and Christian Degen — ETH Zürich, Solid State Physics, Switzerland
Magnetic resonance force microscopy (MRFM) is a scanning probe technique capable of detecting nuclear magnetic resonance (NMR) signals from nanoscale sample volumes. The sample is attached to the cantilever tip and is brought in close proximity to a sub-micrometer sized magnet which provides a magnetic field gradient. Periodic spin inversions synchronized with the cantilever frequency generate an oscillatory force at the tip apex.
The forces generated by nuclear spins in a nanometer-sized volume are on the order of 10 aN and detection requires very compliant cantilevers (spring constant below 10−4 N/m). Though mounted in pendulum geometry, strong interactions between the magnet and the cantilever lead to snap-in distances of tens of nanometers, resonance frequency shifts over one order of magnitude, and significant changes of the effective spring constant even for small scan ranges.
We present our latest setup improvements in order to obtain an artifact-free 3D magnetic resonance image on nanometer scale. This includes the correction of static cantilever deflections as well as the determination of the instantaneous dynamic spring constant, and real-time adjustments of feedback damping parameters.