Magnetization of Nanoparticle Systems in a Rotating Magnetic Field

The investigation of a sizable thermal enhancement of magnetization is put forward for uniaxial ferromagnetic nanoparticles that are placed in a rotating magnetic field. We elucidate the nature of this phenomenon and evaluate the resonant frequency dependence of the induced magnetization. Moreover, we reveal the role of magnetic dipolar interactions, point out potential applications, and reason the feasibility of an experimental observation of this effect.

Figure 1

Sketch of the precession of the up and down magnetic moments (arrows show the directions of their natural precession) at $\rho =-1$.

Figure 2

Plots of ${\mu }_t$ (curve 1), $⟨{\mu }_t⟩$ (curve 2), and ${\mu }_t^{\mathrm{mf}}$ (curve 3) as the functions of the reduced frequency $\tilde{\omega }$.