@article {64902, title = {Parametric amplification of reversible transverse susceptibility in single domain magnetic nanoparticles.}, journal = {AIP Advances}, volume = {9}, year = {2019}, month = {2019 Apr 25}, pages = {045031}, abstract = {
We propose, model, and experimentally demonstrate the enhancement of reversible transverse susceptibility in single domain magnetic nanoparticles through the principle of parametric amplification. It has previously been demonstrated that properly oriented anisotropic single domain magnetic nanoparticles have an appreciable peak in transverse susceptibility at the particle anisotropy field. Here we show theoretically and experimentally that an additional parametric AC magnetic field applied at a proper phase and at twice the frequency (2f) of the transverse field further enhances transverse susceptibility peaks through the process of parametric amplification. We model this effect numerically and describe it through the energy formalism of the single magnetic domain Stoner-Wohlfarth model. The proper phase relationships of the transverse and parametric fields to obtain either parametric amplification or attenuation of the transverse susceptibility signals are also described. We experimentally demonstrate such parametric tuning of transverse susceptibility in single domain magnetic nanoparticles of a commercial audio tape in a prototypical inductive transverse susceptibility set-up.
}, doi = {10.1063/1.5079980}, author = {El Bidweihy, Hatem and Smith, Richard D and Barbic, Mladen} } @article {47876, title = {Effect of magnetic nanoparticle shape on flux amplification in inductive coil magnetic resonance detection.}, journal = {Journal of Applied Physics}, year = {2016}, month = {2016 Sep 14}, pages = {104506-1-7}, abstract = {

We model and analyze the effect of particle shape on the signal amplification in inductive coil magnetic resonance\ detection\ using the reversible transverse\ magnetic susceptibility\ of oriented magnetic nanostructures. Utilizing the single magnetic domain Stoner-Wohlfarth model of uniform magnetization rotation, we reveal that different ellipsoidal particle shapes can have a pronounced effect on the magnetic flux enhancement in\ detection\ configurations typical of magnetic resonance settings. We compare and contrast the prolate ellipsoids, oblate ellipsoids, and exchange-biased spheres and show that the oblate ellipsoids and exchange-biased spheres have a significantly higher flux amplification effect than the prolate ellipsoids considered previously. In addition, oblate ellipsoids have a much broader polarizing\ magnetic fieldrange over which their transverse flux amplification is significant. We show the dependence of transverse flux amplification on magnetic resonance bias field and discuss the resulting signal-to-noise ratio of inductive magnetic resonance\ detection\ due to the magnetic\ nanoparticle-filled\ core of the magnetic resonance\ detection\ coil.

}, doi = {10.1063/1.4962451}, author = {Barbic, Mladen and El Bidweihy, Hatem} }