AC Magnetic Susceptibility of Ferrofluids Exposed to an External Electric Field

Abstract

It is known that ferrofluid superparamagnetic nanoparticles response to external magnetic fields, often resulting in the formation of elongated clusters along the field. This has a notable impact on dielectric properties of ferrofluids. Here we report on indications of a contrary effect when the magnetic susceptibility of ferrofluids based on transformer oil is influenced by an external electric field. This effect is associated with structural changes in the ferrofluids induced by the external electric fields. Particularly, we focus on a steady state electric field effect, which gives rise to forces acting on the magnetite nanoparticles, leading to the formation of aggregates. In this condition we have measured the ferrofluid AC magnetic susceptibility in parallel and perpendicular configuration of magnetic and electric fields at room temperature. The measurements in both configurations yielded a noticeable decrease in the real susceptibility values with increasing electric field intensity. The result is believed to be caused by the reduction in the total magnetic moment of the ferrofluid. This can be a consequence of the superspin interactions in the aggregates, minimizing the aggregate's energy. Finally, we highlight the necessity of NMR and small angle scattering of polarized neutrons investigations in order to obtain exact information on the magnetic structure induced by the electric forces.

Spin Relaxation Effects in Oil-Nanomagnetite Ferrofluids - Mössbauer Spectrometry Studies

“…1) was taken. Final results of TEM photo was already reported in [8]. Mean diameter value of almost spherical magnetite nanoparticles was estimated asd TEM = 10 nm.…”

“…The magnetic ferrofluid was fabricated with commercial transformer oil MOGUL T M and magnetite nanoparticles of about 3% mass concentration utilizing the technological procedure described in [7][8][9]. Examination of the prepared magnetic fluids was done using transmission electron microscopy (TEM), Tesla BS 500 microscope, normally operated at 90 kV with 80,000 magnification by the replication technique.…”

“…These particles are responsible e.g. for very peculiar spin and dielectric relaxation processes, magnetic mesostructuring, as well as change of magnetic and electro-rheological properties under influence of the external electric field [5][6][7][8][9][10].…”