Fabrication and Magnetic Characterization of Permalloy Hemisphere Dot Arrays for Magnonic Metamaterials

Abstract

Metamaterials hold significant promise for applications in microwave devices, particularly in the field of magnonics. This study focuses on the fabrication and magnetic characterization of magnonic metamaterials (MCs) using an array of permalloy (NiFe) hemisphere shells. The NiFe hemisphere shells were fabricated on SU-8 photoresist-coated silicon (Si) substrates via sputtering, resulting in a unique non-planar geometry. This geometric structuring was found to significantly alter the ferromagnetic resonance (FMR) spectra compared to unpatterned NiFe thin films of equivalent thickness. In addition, the magnetization reversal mechanism of the hemisphere dot array was investigated through vibrating sample magnetometry (VSM) and micromagnetic simulations. Our results reveal that the hemisphere dot array exhibits reduced magnetic anisotropy and a lower coercive field compared to pure NiFe films. The hysteresis loops obtained from micromagnetic simulations indicate the presence of a vortex magnetization configuration within the hemispherical structure. This study highlights the crucial role of geometry in determining the magnetic properties of curved nanostructures, which is essential for the advancement of next-generation magnonic devices. By examining the influence of the thickness-to-diameter ratio on the FMR spectra and overall magnetic behavior, we demonstrate the potential of these nanostructures to serve as tailored MCs. Our findings contribute to the broader field of spintronics, where the control of spin waves in engineered materials is vital for future innovations in information processing and storage. This research underscores the impact of geometric design on the magnetic properties of metamaterials, offering new possibilities for their application in advanced microwave technologies.