Vibrational response of FeNi3 nanoparticles to the flux of a modulated electromagnetic field detected by contact-mode atomic force microscopy

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A hybrid imaging mode was developed for characterizing samples of magnetic FeNi3 nanoparticles, which combines contact-mode atomic force microscopy (AFM) with magnetic modulation of samples. For conventional magnetic imaging modes of AFM, magnetically coated tips are used directly as a sensor to measure the relatively long-range forces of magnetic samples in a noncontact configuration. For the magnetic sample modulation (MSM) configuration, however, the changes in sample dynamics form the basis for measurements of material properties using contact-mode AFM. Nanoparticles are driven to vibrate in response to an externally applied electromagnetic field, and a nonmagnetic tip is used as a motion sensor for directly mapping the vibration with contact-mode. Intermetallic nanoparticles of FeNi3 were used as a model nanomaterial, synthesized by either conventional oven heating or microwave preparation. By slowly scanning an AFM probe across vibrating nanoparticles, changes in the frequency and amplitude of the sample motion can be sensitively tracked by the deflection of an AFM probe. Thus, the nonmagnetic AFM tip provides a force and motion sensor for mapping the vibrational response of magnetic nanomaterials at the level of individual nanoparticles. Dynamic protocols were developed for systematic studies with changes in the magnetic field strength and field frequency. © 2013 American Chemical Society.

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Journal of Physical Chemistry C

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