Ferromagnetic resonance of a magnetic dimer with dipolar coupling

TL;DR

This paper presents a comprehensive formalism for analyzing ferromagnetic resonance in magnetic dimers with dipolar coupling, accounting for finite size, aspect ratio, and anisotropy, providing analytical and numerical insights into resonance behavior.

Contribution

It introduces a general analytical framework for ferromagnetic resonance in coupled nanomagnet dimers, considering various configurations and anisotropies, advancing understanding of their dynamic properties.

Findings

Resonance frequency depends on applied field, coupling, and anisotropy.

Critical field for resonance frequency vanishing varies with coupling and aspect ratio.

Results aid in characterizing anisotropy and coupling in nanomagnet systems.

Abstract

We develop a general formalism for analyzing the ferromagnetic resonance characteristics of a magnetic dimer consisting of two magnetic elements (in a horizontal or vertical configuration) coupled by dipolar interaction, taking account of their finite-size and aspect ratio. We study the effect on the resonance frequency and resonance field of the applied magnetic field (in amplitude and direction), the inter-element coupling, and the uniaxial anisotropy in various configurations. We obtain analytical expressions for the resonance frequency in various regimes of the interlayer coupling. We (numerically) investigate the behavior of the resonance field in the corresponding regimes. The critical value of the applied magnetic field at which the resonance frequency vanishes may be an increasing or a decreasing function of the dimer's coupling, depending on the anisotropy configuration. It is also a function of the nanomagnets aspect ratio in the case of in-plane anisotropy. This and several other results of this work, when compared with experiments using the standard ferromagnetic resonance with fixed frequency, or the network analyzer with varying frequency and applied magnetic field, provide a useful means for characterizing the effective anisotropy and coupling within systems of stacked or assembled nanomagnets.