Nonlinear Phenomena in Magnetic Nanoparticle Systems at Microwave Frequencies

Nonlinear interactions of electromagnetic waves (EMW) in magnetic nanoparticle systems at microwave frequencies were numerically simulated using rigorous mathematical models to solve the nonlinear diffraction boundary problem. The transmission coefficients |S₁₂| of arrays of ferrite spheres, depending on the normalized frequency omega/gamma (gamma gyromagnetic ratio), for radii of 250 mm and 0.1 mm, and separation between the spheres from 600 to 3000 nm, were determined. The increase of the interaction effects upon decreasing separation is demonstrated. The instability regions of parametric generation in the nonlinear ferrite sphere array, depending on the magnitude of the pumping wave at frequency omega_H, are simulated using our computational algorithm of the bifurcation points of the nonlinear Maxwell´s operator. With decreasing separation, i.e., increasing interaction between the spherical elements of the array, the instabilities occur at lower inputs, revealing the power sensitivity of small particle systems.