Ferromagnetic resonance of a two-dimensional array of nanomagnets: Effects of surface anisotropy and dipolar interactions

Abstract

We develop an analytical approach for studying the FMR frequency shift due to dipolar interactions and surface effects in two-dimensional arrays of nanomagnets with (effective) uniaxial anisotropy along the magnetic field. For this we build a general formalism on the basis of perturbation theory that applies to dilute assemblies but which goes beyond the point-dipole approximation as it takes account of the size and shape of the nano-elements, in addition to their separation and spatial arrangement. The contribution to the frequency shift due to the shape and size of the nano-elements has been obtained in terms of their aspect ratio, their separation and the lattice geometry. We have also varied the size of the array itself and compared the results with a semi-analytical model and reached an agreement that improves as the size of the array increases. We find that the red-shift of the ferromagnetic resonance due to dipolar interactions decreases for smaller arrays. Surface effects may induce either a blue-shift or a red-shift of the FMR frequency, depending on the crystal and magnetic properties of the nano-elements themselves. In particular, some configurations of the nano-elements assemblies may lead to a full compensation between surface effects and dipole interactions.

arXiv comment14 pages, 5 figures

References in corpus (13)

• Surface contribution to the anisotropy of magnetic nanoparticles
• Effective anisotropies and energy barriers of magnetic nanoparticles with Neel surface anisotropy
• Identification and selection rules of the spin-wave eigen-modes in a normally magnetized nano-pillar
• Surface-induced cubic anisotropy in nanomagnets
• Spin torque ferromagnetic resonance with magnetic field modulation
• Measurement of the dynamical dipolar coupling in a pair of magnetic nano-disks using a Ferromagnetic Resonance Force Microscope
• Thermodynamic perturbation theory for dipolar superparamagnets
• Effects of spin non-collinearities in magnetic nanoparticles
• Interplay between surface anisotropy and dipolar interactions in an assembly of nanomagnets
• AC susceptibility of an assembly of nanomagnets: combined effects of surface anisotropy and dipolar interactions
• Dipole-dipole interaction in arrays of Fe/Fe${}_x$O${}_y$ core/shell nanocubes probed by ferromagnetic resonance
• Ferromagnetic resonance of a magnetic dimer with dipolar coupling
• Surface effects on ferromagnetic resonance in magnetic nanocubes

Cited by in corpus (4)

• Bifurcation structure and chaos in nanomagnet coupled to Josephson junction
• Dipolar Interaction and Sample Shape Effects on the Hysteresis Properties of 2d Array of Magnetic Nanoparticles
• Single-particle versus collective effects in assemblies of nanomagnets: screening
• Resonance phenomena in a nanomagnet coupled to a Josephson junction under external periodic drive