Nanostructured Magnonic Crystals with Size-Tunable Bandgaps

Abstract

Just as a photonic crystal is a periodic composite composed of materials with different dielectric constants, its lesser known magnetic analogue, the magnonic crystal can be considered as a periodic composite comprising different magnetic materials. Magnonic crystals are excellent candidates for the fabrication of nanoscale microwave devices, as the wavelengths of magnons in magnonic crystals are orders of magnitude shorter than those of photons, of the same frequency, in photonic crystals. Using advanced electron beam lithographic techniques, we have fabricated a series of novel bicomponent magnonic crystals which exhibit well-defined frequency bandgaps. They are in the form of laterally patterned periodic arrays of alternating cobalt and permalloy stripes of various widths ranging from 150 to 500 nm. Investigations by Brillouin light scattering and computer modeling show that the dispersion spectrum of these crystals is strongly dependent on their structural dimensions. For instance, their first frequency bandgap is found to vary over a wide range of 1.4-2.6 gigahertz. Such a functionality permits the tailoring of the bandgap structure which controls the transmission of information-carrying spin waves in devices based on these crystals. Additionally, it is observed that the bandgap width decreases with increasing permalloy stripe width, but increases with increasing cobalt stripe width, and that the bandgap center frequency is more dependent on the stripe width of permalloy than that of cobalt. This information would be of value in the design of magnonic crystals for potential applications in the emerging field of magnonics.

Odd−Even Effects in Charge Transport across Self-Assembled Monolayers

“…log(|J|/[A/cm 2 ], written as log(|J|) for convenience, was normally distributed). Log-normal distributions of current have been observed previously in molecular junctions by us (using Hg-drop junctions) 78 and others (using polymer buffer layers, 63,106,130 nanopores, 60,136,137 and cpAFM [138][139][140] ). In all of these studies, the explanation for the apparent normal distribution of log(|J|) is that J depends exponentially on a physical parameter that is normally distributed, such as the thickness of the tunneling barrier between two electrodes.…”

Spin inelastic currents in molecular ring junctions

“…Refs. 93,94), and should be expected also in the spin-flip IETS. Since external magnetic field is a simpler control than either gate potential or molecule-contacts coupling strength observation of transition between the two types of the IETS signal should be easier for spin-flip IETS .…”

Reconfigurable wave band structure of an artificial square ice

“…The term magnonics has been coined to describe this field of study [5,6]. One pathway to control magnon dispersions is to construct magnonic crystals [7,8] that are metamaterials with a spatial modulation of the magnetic properties on length scales comparable to relevant magnonic wavelengths [9][10][11]. Patterned thin magnetic films [12,13] or topographically modulated thin films have been used to manipulate the magnon spectra [14].…”