  We present a systematic micromagnetic study of standing spin-wave modes in
infinitely long Permalloy strips with rectangular cross-section. Using a
finite-element dynamic-matrix method, we first calculate the eigenfrequencies
and the corresponding eigenvectors (mode profiles), as a function of the
in-plane magnetic field applied across the strip. The ferromagnetic resonance
spectra is computed from the mode profiles, assuming a homogeneous
radio-frequency excitation, equivalently to an experimental ferromagnetic
resonance measurement. The investigation of the field-dependent mode profiles
enables for the classification of the observed resonances, here focusing mostly
on the true edge mode localized at the vicinity of strip edges. Furthermore, we
study the mode localization in pairs of 50-nm-thick Permalloy strips as a
function of the strip width and their lateral separation. For closely spaced
strips, the spatial profile of the quasi-uniform mode is substantially modified
due to a significant hybridization with the edge-localized standing spin-wave
modes of the neighbouring strip. We show that a wide-range-tunability of the
localized edge-mode resonances can be achieved with a precise control of the
magnetostatic coupling between the strips. Extreme sensitivity of the edge mode
frequency on the bias field demonstrates a potential of the edge resonances for
field sensing. Furthermore, for narrow strips (~100 nm in width), due to the
reduced number of the allowed confined modes, a field-controllable switching
between the resonances localized either in the strip center or at the edges of
the strips can be achieved.
