Abstract
Multiwall carbon nanotubes (MWCNTs) fabricated by chemical vapor deposition contain magnetic nanoparticles. While increasing frequency of electromagnetic field (EMF) exposure (up to <10 kHz) of MWCNTs resulted in slight induced magnetization decrease due to skin effect of the conducting carbon, we discovered that higher frequencies (>10 kHz) contained an exponential magnetization increase. We show that puzzling magnetization increase with decreasing magnetic field amplitude (less than 0.5 A/m for 512 kHz) is due to matching the field amplitudes of the magnetic nanoparticles inside nanotubes. This observation reveals a possibility of magnetic tunneling in MWCNTs (change of magnetic state of blocked magnetic moments). This interpretation is supported by observation of unblocking larger magnetic remanence (MR) portion from MWCNTs with progressively smaller amplitude of oscillating magnetic field.
Highlights
Multiwall carbon nanotubes (MWCNTs) fabricated by chemical vapor deposition contain magnetic nanoparticles
(4 cm × 2.5 cm radius) container was exposed to variation of electromagnetic field (EMF) (Fig. 3)
EMFs with >10 kHz, showed exponential susceptibility increase that continued beyond 512 KHz (Fig. 4)
Summary
Multiwall carbon nanotubes (MWCNTs) fabricated by chemical vapor deposition contain magnetic nanoparticles. We show that puzzling magnetization increase with decreasing magnetic field amplitude (less than 0.5 A/m for 512 kHz) is due to matching the field amplitudes of the magnetic nanoparticles inside nanotubes This observation reveals a possibility of magnetic tunneling in MWCNTs (change of magnetic state of blocked magnetic moments). Spinnable multiwall carbon nanotubes (MWCNTs) contain multiple (up to 100) conducting graphene walls and provide an unusual conducting structure that may be utilized in development of new materials. We chose this material because of an unknown and unresearched response of these MWCNT structures to high frequency oscillating magnetic fields. Magnetic moment is blocked for that time period and the probability of crossing the barrier from one magnetic state to the other becomes increasingly lower
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