  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.
