Ferromagnetic resonance of magnetostatically coupled shifted chains of nanoparticles in an oblique magnetic field

We investigate the ferromagnetic resonance characteristics of a magnetic dimer composed of two shifted parallel chains of iron nanoparticles coupled with dipolar interactions. The latter are treated beyond the point-dipole approximation, taking into account the finite size and arbitrary shape of the nano-elements and arbitrary separation. The resonance frequency is calculated as a function of the amplitude of the applied magnetic field, and the resonance field is computed as a function of the direction of the applied field, varied both in the plane of the two chains and perpendicular to it. We highlight a critical value of the magnetic field which marks a state transition that should be important in magnetic recording media.