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.
Highlights
Fabrication, characterization, and applications of magnetic nanoparticles continue to receive significant attention due to their interesting fundamental scientific properties as well as their enormous applicability in various technologies, such as the magnetic information data storage,1,2 biomedical applications,3,4 and fundamental thermodynamics of computation.5–8 For nanometer scale magnetic particles, formation of magnetic domain walls within the particle becomes energetically unfavorable, and magnetic moments within the nanoparticle remain aligned and change direction only by uniform coherent rotation
Those studies often reveal that oriented anisotropic single domain magnetic nanoparticles have an appreciable peak in χX at large values of the perpendicular DC magnetic field BZdc, and represent good candidates for amplifying transverse alternating magnetic fields in magnetic resonance experiments
We demonstrate both theoretically and experimentally that an additional “pump” AC magnetic field along the z-axis at twice the frequency of the driving transverse AC magnetic field along the x-axis amplifies or attenuates transverse susceptibility depending on the proper phase of the “pump” magnetic field
Summary
Scitation.org/journal/adv method to further manipulate transverse susceptibility through the principle of parametric amplification. We demonstrate both theoretically and experimentally that an additional “pump” AC magnetic field along the z-axis at twice the frequency of the driving transverse AC magnetic field along the x-axis amplifies or attenuates transverse susceptibility depending on the proper phase of the “pump” magnetic field. We explain the principles of such parametric amplification through the energy diagrams of the Stoner-Wohlfarth model of a single domain magnetic particle
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