Laboratoire de Physique et Chimie des Nano-objets

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Home page > LPCNO > Groups > Nanomagnetism > Main research topics > Carbon Nanotube Electromechanical Resonators: Towards Unique Magnetic Nanoparticle Measurements

Carbon Nanotube Electromechanical Resonators: Towards Unique Magnetic Nanoparticle Measurements

The project we propose, aims to develop and to optimize carbon nanotube electromechanical resonators for ultra sensitive magnetic measurements. With this new and original approach we want to directly measure the hysteresis magnetic loop on a broad temperature and magnetic field range of one chemically synthesized nano-object as nanoparticles with very small size (d 1nm) and small magnetization or molecular magnets. This measurement technique should allow us to better understand the fundamental magnetic properties as anisotropy, absolute magnetization and switching magnetic field mechanisms at the nanoscale. Since yet, no magnetic measurement techniques have the sensitivity to characterize one individual nanoparticle with a magnetic moment below few 100 µB.

a) Scanning electronic microscopy image of a carbon nanotube electromechanical resonator. The carbon nanotube is pointed by a white arrow. b) Schematic of the electrical connexions which enable to actuate and detect the mechanical motion of the carbon nanotube. The nanoparticle has a magnetization . Under a magnetic field, it is submitted to a magnetic torque which stresses the carbon nanotube. c) et d) Theoretical calculation of the carbon nanotube mechanical resonant frequency shift under magnetic field (red curve). We consider that the nanoparticle is single domain and its magnetization rotates coherently under magnetic field (black curve).

Carbon nanotube electromechanical resonators (cf figure a) have recently shown a great potential as ultrasensitive mass or force sensors [1]. They have allowed to weigh the mass of very few atoms [1,2] at low temperature. They overcome by a factor of 10 000 the best microfabricated silicon beams made so far.

To measure the nanoparticle magnetic properties with a carbon nanotube, the nanoparticle should be primarily chemically grafted on the carbon nanotube surface (cf figure b) by using for example electrospray technique (in development). Then, the magnetic interaction between the magnetic field and the nanoparticle is studied through the mechanical properties of the carbon nanotube which are affected by the magnetic torque appearing on the nanoparticle (figure c et d). Preliminary theoretical predictions have shown that carbon nanotubes could reach exceptional sensitivity at low temperature of the order of the Bohr magneton.

- [1] B. Lassagne & col, Nano Lett. 8 , 3735 (2008), B. Lassagne & col, Science, 325, 1107 (2009).
- [2] K. Jensen & col, Nature Nanotech. 3, 533 (2008), Chiu, & col, Nano Letters. 8, 4342 (2008).