Abstract
<title>Abstract</title> <p>Engineering spin-wave spectra without modifying device geometry remains a central challenge in magnonics. Here, we investigate how longitudinal compositional interfaces reshape the equilibrium magnetic configurations and spin-wave dynamics of homogeneous and multisegmented Co/CoNi/Ni nanowires using micromagnetic simulations. We demonstrate that compo-sitional interfaces reorganize the magnetic energy landscape, stabilizing hybrid magnetic configurations that reorganize the spin-wave eigenmode spectrum through mode hybridization, localization, and spectral-weight transfer. Rather than generating additional resonances, increasing the interface density continuously shifts the dominant microwave response from the C band of Ni nanowires toward the Ku band of Co nanowires, while multisegmented architectures naturally stabilize resonances within the technologically relevant X band. These findings establish longitudinal compositional interfaces as an independent design parameter for programming spin-wave spectra and engineering reconfigurable magnonic and microwave nanodevices.</p>