Map of metastable states for thin circular magnetic nano-cylinders

Nano-magnetic systems of artificially shaped ferromagnetic islands, recently became a popular subject due to their current and potential applications in spintronics, magneto-photonics and superconductivity. When the island size is close to the exchange length of magnetic material (around 15 nm), its magnetic structure becomes markedly different. It determines both static and dynamic magnetic properties of elements, but strongly depends on their shape and size. Here we map this dependence for circular cylindrical islands of a few exchange lengths in size. We outline the region of metastability of "C"-type magnetic states, proving that they are indeed genuine and not a result of pinning on particle imperfections. A way to create the smallest particles with guaranteed magnetic vortex state at zero field becomes evident. It is expected that the map will help focus the efforts in planning of experiments and devices.Comment: 3 pages, 1 figur

HORIZONTALLY PLASMON HYBRIDIZATION ON SYMMETRIC-BREAKING METAMATERIALS

In this report, we present a study on the fundamental negative-permeability metamaterials, named as the cut-wire-pair structure. The physics of the cut-wire-pair metamaterial is interpreted using the electromagnetic analog of molecular-orbital theory. It is shown that a symmetric-breaking cut-wire-pair metamaterial is horizontally plasmon-hybridized, leading to an additional magnetic resonance beyond the conventional one. The transmission spectra and the induced energy distributions are performed to demonstrate our prediction

High-Performance and Flexible Metamaterial Wave Absorbers with Specific Bandwidths for the Microwave Device

In this paper, we proposed a high-performance electromagnetic-wave metamaterial absorber which can be used directly for 5G technology. The absorber exhibits a high performance in a tailored frequency range of 28 ± 1 GHz. At both transverse-electric and transverse-magnetic polarization, the absorption exceeds 99% when the electromagnetic wave is incident normally, and the absorption keeps being over 97% as the incident angle increases even to 45 degrees. The absorber is flexible, and it is very suitable for mass production because the production process is simple. In addition, the minimum dimension of the meta-structure is only 0.2 mm, and the cost is relatively low. Similarly, another high-performance metamaterial absorber with a tailored bandwidth at the center frequency of 77 GHz, which is relevant to self-driving cars, was also prepared by a minimal adjustment to the original structure

Dual-Band Unidirectional Reflectionless Propagation in Metamaterial Based on Two Circular-Hole Resonators

Dual-band unidirectional reflectionless propagation at two exceptional points is investigated in metamaterial, which is composed of only two gold resonators with circular holes, by simply manipulating the angle of incident wave and distance between two resonators. Furthermore, the dual-band unidirectional reflectionless propagation can be realized in the wide ranges of incident angle from 0 ∘ to 50 ∘ and distance from 255 nm to 355 nm between two resonators. In addition, our scheme is insensitive to polarization of incident wave due to the circular-hole structure of the resonators

Metamaterial-enhanced vibrational absorption spectroscopy for the detection of protein molecules

From visible to mid-infrared frequencies, molecular sensing has been a major successful application of plasmonics because of the enormous enhancement of the surface electromagnetic nearfield associated with the induced collective motion of surface free carriers excited by the probe light. However, in the lower-energy terahertz (THz) region, sensing by detecting molecular vibrations is still challenging because of low sensitivity, complicated spectral features, and relatively little accumulated knowledge of molecules. Here, we report the use of a micron-scale thin-slab metamaterial (MM) architecture, which functions as an amplifier for enhancing the absorption signal of the THz vibration of an ultrathin adsorbed layer of large organic molecules. We examined bovine serum albumin (BSA) as a prototype large protein molecule and Rhodamine 6G (Rh6G) and 3,3'-diethylthiatricarbocyanine iodide (DTTCI) as examples of small molecules. Among them, our MM significantly magnified only the signal strength of bulky BSA. On the other hand, DTTCI and Rh6G are inactive, as they lack low-frequency vibrational modes in this frequency region. The results obtained here clearly demonstrate the promise of MM-enhanced absorption spectroscopy in the THz region for detection and structural monitoring of large biomolecules such as proteins or pathogenic enzymes

Strain Sensitivity of Electric-Magnetic Coupling in Flexible Terahertz Metamaterials

In order to investigate the effects of bending strain on electric-magnetic coupling, we fabricated and characterized two types of flexible terahertz (THz) metamaterials on polyethylene naphthalate (PEN) substrates, which had either asymmetric or symmetric configuration. The asymmetric flexible THz metamaterials showed a plasmon-induced transparency originating from electric-magnetic coupling. The transparency was rather robust and insensitive to strain. The symmetric metamaterials demonstrated a transmission dip at a frequency of 1.35 THz without applied strain due to electric resonance. However, if strain gradually varied, a continuously tunable transmission dip was observed at a frequency of 1.1 THz, which could be ascribed to electric-magnetic coupling induced by symmetry breaking. The promising results suggested that the asymmetric and the symmetric flexible THz metamaterials could find potential applications in curved devices and remote stress sensors, respectively